All Wired Up: What You Should Know About Spark Plug Wires in Your Harley-Davidson (+ 5 Replacement Kit Options)

The evolution of spark plug wires, which we now recognize as the modern incarnation, traces its roots back almost a century ago. However, it is important to note that the spark plug wire of yesteryears bore little resemblance to its present form. During the early 1900s, spark plug wires initially took the shape of simple metal straps. However, the ever-increasing demand for electronic components in vehicles prompted a transformation in their design and construction.

Transitioning from metal straps, spark plug wires underwent a significant metamorphosis, adopting a cotton-wrapped, lacquered cable structure with a sturdy metal core. This new design was engineered to withstand the high voltage demands of the engines they were utilized in. As the landscape of motorcycle and engine technologies continued to evolve and improve, the demands placed on spark plugs and spark plug wires increased proportionally. Consequently, manufacturers began implementing further advancements in spark plug wire manufacturing processes, ultimately resulting in the rubbery noodle-like appearance that characterizes contemporary spark plug wires.

Now, if you find yourself nearing a service interval for your beloved Harley-Davidson motorcycle, contemplating the imminent task of replacing your spark plug wires, you may be pondering which spark plug wires would be the ideal choice for your specific needs. Additionally, you may be curious as to whether installing larger spark plug wires could truly enhance the performance and overall running efficiency of your motorcycle. Fear not, as this article aims to delve deep into the realm of spark plugs, elucidating their function within your motor, highlighting key differences among various options, and providing valuable insights on when to identify the need for spark plug wire replacement.

Moreover, we shall explore the diverse range of replacement options available to you when embarking on the quest for a new set of spark plug wires tailored specifically for your prized Harley-Davidson motorcycle. By understanding the significance of spark plugs and spark plug wires in optimizing your motorcycle’s performance, you will be equipped with the knowledge needed to make an informed decision regarding your replacement spark plug wire selection. So, let us embark on this journey together and unravel the mysteries surrounding spark plug wires for Harley-Davidson motorcycles.

A refresher on what spark plug wires do…

Spark plug wires play a crucial role in the functioning of Harley-Davidson motorcycles, acting as essential conduits that facilitate the transfer of electrical energy within the ignition system. Serving as the vital link between the coil, intricately integrated with the motorcycle’s electrical system, and the spark plug itself, these wires serve as the conduit for the voltage required to ignite the air-fuel mixture within the cylinder.

Positioned from the coil to the end of the spark plug protruding from the cylinder, these wires establish a vital bridge, enabling the transmission of the voltage generated by the ignition coil or magneto towards the spark plug. With one end connected to the spark plug, which extends outward from the cylinder, the other end resides within the combustion chamber, encompassing a precise blend of air and fuel.

As the voltage surges through the spark plug wire, it embarks on a transformative journey, fulfilling the critical task of delivering the final spark needed to initiate combustion within the cylinder. The seamless transmission of this electrical energy through the wire and into the spark plug sets the stage for the creation of an explosive reaction, ultimately powering the motorcycle.

Harley-Davidson motorcycles rely on the meticulous synchronization between the coil, spark plug wire, and spark plug, as each component plays an indispensable role in the ignition process. The spark plug wire acts as a lifeline, guiding the electrical potential from the coil or magneto to the spark plug, thus serving as a catalyst for the combustion that propels the engine.

To optimize the performance and efficiency of a Harley-Davidson motorcycle, it is imperative to ensure the spark plug wires are in optimal condition, free from any damage or wear that could hinder the smooth flow of electrical energy. Regular inspection and maintenance of these wires not only guarantee a reliable ignition system but also contribute to the overall longevity and performance of the motorcycle.

As an expert in the realm of Harley-Davidson motorcycles, I emphasize the significance of understanding the intricate interplay between the coil, spark plug wire, and spark plug. Acknowledging the vital role played by the spark plug wire and its ability to facilitate the transfer of voltage, enthusiasts can appreciate the complex symphony of elements that power these iconic motorcycles. From the initial electrical ignition to the roaring engine, every element works in harmony, with the spark plug wire acting as a conduit for the transformative energy that propels the exhilarating journey ahead.

How do I know if my spark plug wires are bad?

As a passionate Harley-Davidson enthusiast, I can attest to the importance of spark plug wires in maintaining optimal performance and combustion efficiency. Over time, these wires are prone to deterioration and wear, leading to potential issues. A deteriorated or fouled spark plug can cause a misfire, disrupting the engine’s smooth operation and hindering its ability to run or idle seamlessly. This occurs when the combustion process in the cylinder is compromised due to the inability of the voltage to travel successfully through the plug, consequently failing to ignite the fuel.

Fortunately, there are clear indicators that can alert riders to the presence of faulty spark plug wires. Similar to the symptoms associated with a fouled spark plug, engine performance becomes a telltale sign. A sudden, unsteady idle becomes apparent as a result of the compromised combustion process, as the voltage struggles to travel through the faulty wire. Additionally, engine backfiring and reduced acceleration may become noticeable, indicating that the spark plug wires are impeding the optimal functioning of the engine. Another consequence of deteriorated spark plug wires is a decline in fuel efficiency, as the engine operates less efficiently than it should. Upon closer inspection, visible damage to the spark plug wires, such as scorch marks, melting caused by improper seating or overheating, or physical damage like nicks and cuts in the insulation, may be observed. These damages further hinder the wire’s ability to successfully carry a voltage current, exacerbating the performance issues.

When contemplating spark plug replacement, motorcycle owners should also consider replacing the spark plug wires simultaneously, even if no obvious damage or wear is present. From a maintenance standpoint, it is prudent to replace both components together. Since the spark plug wires need to be disconnected to replace the spark plugs, replacing them at the same time ensures a fresh and efficient system. This approach significantly reduces the likelihood of experiencing misfire situations that can occur when reusing old or worn spark plug wires.

In summary, the importance of spark plug wires in maintaining a Harley-Davidson motorcycle’s performance cannot be overstated. Regular inspection and timely replacement of these wires, in conjunction with spark plug maintenance, is crucial to ensure a smooth-running engine, optimal combustion, and enhanced fuel efficiency. By adhering to these practices, Harley-Davidson riders can experience the thrill of the open road with confidence, knowing that their beloved motorcycles are operating at their best.

Shopping for Replacement Spark Plug Wire Kits

In this section, we will delve into an array of meticulously crafted spark plug wire alternatives that are readily accessible for purchase, encompassing an extensive examination of the distinctive features and advantages they bring forth. As an impassioned connoisseur of the illustrious Harley-Davidson brand, allow me to illuminate your path towards the optimal selection, tailored specifically to cater to the distinctive intricacies of various Harley-Davidson engines. Prepare to embark on a journey through a myriad of options, all conveniently available for acquisition on the esteemed platform of Amazon.

To commence this expedition, let us begin with an exploration of a renowned and widely acclaimed brand in the realm of spark plug wires: Dragon Fire. Synonymous with excellence, Dragon Fire spark plug wires offer a comprehensive range of replacement options that are meticulously engineered to enhance the performance and reliability of your beloved Harley-Davidson motorcycle. These remarkable wire sets have been meticulously crafted with an unwavering commitment to quality, delivering unparalleled levels of conductivity and ensuring optimal spark delivery to ignite the fiery potential of your engine.

Before we embark on an exploration of alternative options, it is worth noting that each of the spark plug wire sets we shall discuss can be conveniently procured on the esteemed platform of Amazon. Furthermore, it is of utmost importance to emphasize that these wire sets are intelligently designed and pre-determined in custom lengths, alleviating the need for intricate measurements or arduous crimping procedures upon their arrival at your doorstep. Rest assured, with diligent verification of engine compatibility on the listing site, a seamless installation experience awaits you.

Now, let us expand our horizons and delve into the captivating realm of alternative spark plug wire options that stand as viable contenders for your cherished Harley-Davidson machine. While Dragon Fire has already captivated our attention, it would be remiss not to explore the myriad of other possibilities that exist within the marketplace.

In this vast landscape of options, discerning riders may find solace in the embrace of other distinguished brands, each with their unique offerings. Diving deeper, you may encounter renowned manufacturers who have carved their own path in the pursuit of excellence, diligently crafting spark plug wires that cater to the diverse needs of Harley-Davidson enthusiasts.

Through meticulous research and dedication to the pursuit of unrivaled performance, these alternative options have honed their craft to deliver unparalleled levels of reliability and efficiency. With a harmonious blend of cutting-edge technology, premium materials, and astute engineering prowess, these manufacturers have managed to manifest spark plug wires that seamlessly integrate with a multitude of Harley-Davidson engines, ensuring optimal functionality and unleashing the untamed potential that lies within.

As you traverse this captivating domain of spark plug wire alternatives, allow your discerning instincts to guide you towards the perfect synergy between your motorcycle’s distinctive engine specifications and the unrivaled prowess of these meticulously designed wire sets. By harmonizing form and function, these alternative options stand poised to elevate your riding experience to unprecedented heights, ensuring that every twist of the throttle ignites a symphony of power, precision, and unyielding passion.

In conclusion, fellow devotees of the iconic Harley-Davidson legacy, I implore you to embark on this enchanting expedition, exploring the realms of spark plug wire options with an insatiable hunger for excellence. Whether you choose to embark on the path paved by the esteemed Dragon Fire brand or venture into uncharted territories of alternative manufacturers, may your journey be one filled with unparalleled performance, reliability, and an unwavering connection to the soul of your Harley-Davidson machine. Remember, each spark plug wire set beckons you towards a realm where power meets passion, and where the symphony of your engine’s roar resonates with the very essence of freedom on the open road.


These premium spark plug wires have been meticulously crafted to meet the precise specifications required for optimal performance in various Harley-Davidson big twin 103 motor applications. However, it’s important to note that this specific kit has been designed with a targeted focus on compatibility with 1999-2017 Dyna engines, ensuring a seamless fit and superior functionality.

One of the standout features of these spark plug wires is their construction. They boast a Kevlar core, renowned for its exceptional strength and durability, paired with a high-quality copper-nickel conductor. This combination guarantees efficient energy transfer, enabling consistent and reliable ignition throughout the engine.

To further enhance their reliability, these wires are encased in a premium silicone sleeve. This sleeve not only provides excellent heat resistance up to an impressive 600°F but also offers exceptional insulation, protecting the wires from potential electrical interference and external damage. This level of protection ensures that the spark plug wires maintain their integrity even in demanding riding conditions.

Additionally, these wires have been expertly cut to the appropriate lengths for the specified Dyna model engines manufactured between 1999 and 2017. The kit includes two spark plug wires, with one wire measuring 8 inches and the other 20 inches in length. This precision in sizing guarantees a perfect fit, eliminating any potential installation difficulties and ensuring optimal performance.

When it comes to electrical resistance, these spark plug wires deliver remarkable results. With a core wire resistance advertised at an impressive 150 ohms per foot, they effectively minimize energy loss, maximizing the power delivered to the spark plugs. This results in improved ignition efficiency and enhanced overall engine performance.

Offered as a comprehensive kit, these high-quality spark plug wires can be yours for an affordable price of approximately $39.95 USD. This budget-friendly package includes two spark plug wires, providing exceptional value for Harley-Davidson enthusiasts looking to optimize their Dyna engines’ performance without breaking the bank.

In conclusion, these meticulously engineered spark plug wires are the epitome of excellence for Harley-Davidson enthusiasts seeking enhanced ignition performance. Designed to precise specifications, featuring a durable construction, optimal length, and impressive electrical resistance, these wires are a must-have for anyone looking to maximize the potential of their 1999-2017 Dyna engines. Invest in these top-of-the-line spark plug wires and experience the true power and reliability that Harley-Davidson is renowned for.


Introducing the new line of spark plug wires specifically designed for Harley-Davidson enthusiasts! These exceptional wires are meticulously crafted to cater to the unique needs of 2009 to 2016 Touring and Trike motors, offering longer wire lengths for seamless installation. With a promise of a direct factory fit, these wires have become the go-to choice for riders seeking unparalleled performance.

One of the key features of these extraordinary spark plug wires lies in their construction. Each wire boasts a copper-nickel alloy conductor, a cutting-edge material known for its exceptional conductivity and durability. This conductor is skillfully nestled beneath a robust Kevlar layer, providing utmost protection against the rigors of the road. Additionally, an extra layer of fiberglass insulation further enhances the wires’ resilience, ensuring reliable performance even in demanding riding conditions. Like the previously reviewed spark plug wires, the outer silicone sleeve undergoes rigorous testing and can withstand temperatures of up to an impressive 600 degrees Fahrenheit.

In terms of technical specifications, these wires proudly offer a core wire resistance of 150 ohms per foot, guaranteeing optimal electrical flow and facilitating efficient combustion. This characteristic plays a crucial role in maximizing the performance potential of your beloved Harley-Davidson motorcycle.

Adding a touch of personalization, these remarkable wires are available in a variety of vibrant colors, allowing you to effortlessly match your motorcycle’s color scheme. Whether you prefer the boldness of red, the vibrancy of yellow, or the timeless elegance of transparent red, these wires offer a perfect complement to your bike’s aesthetics.

Understanding the needs of Harley-Davidson riders, each kit comprises a set of two spark plug wires, ensuring comprehensive coverage for your engine. Priced at an incredibly reasonable ~$39.95 USD, this kit represents an outstanding value for the discerning motorcycle enthusiast.

Investing in these top-of-the-line spark plug wires is not just about aesthetics or customization; it’s about elevating your Harley-Davidson experience to a whole new level. By incorporating these wires into your motorcycle, you can enjoy enhanced performance, improved ignition efficiency, and ultimately, a smoother and more exhilarating ride.

Trust in the expertise and dedication of our Harley-Davidson specialists, who have meticulously designed and engineered these spark plug wires to exceed your expectations. Join the countless riders who have already embraced this revolutionary product and take your Harley-Davidson journey to unprecedented heights. Order your set of these exceptional spark plug wires today and witness the remarkable difference they can make in your riding experience.


Similar to the AIP spark plug wires, this particular set is specifically designed to cater to the needs of big twin 103 motors produced between 1999 and 2017, showcasing a remarkable compatibility. These high-quality wires also possess a sturdy 10mm thickness, ensuring durability and optimal performance. As a testament to the brand’s commitment to customization, enthusiasts have the liberty to choose between vibrant red or bold blue options, enabling them to align their motorcycle’s aesthetic with their personal taste and style.

For those with engines that necessitate the use of 8mm spark plug wires, fret not, as a supplementary set of 8mm cables is also available. This remarkable attention to detail exemplifies the brand’s dedication to meeting the diverse requirements of Harley-Davidson owners.

One of the notable advantages of this set of spark plug wires is the convenience it offers. Unlike other alternatives, these wires are meticulously custom-cut and pre-crimped with boots, sparing enthusiasts the hassle of measuring and fabricating the wire ends themselves. This user-friendly feature enables riders to seamlessly install the wires, allowing them to spend more time on the road and less time on complex installations.

However, it is worth mentioning that unlike the Dragon Fire spark plug wire kits, these particular wires do not seem to incorporate additional sleeves or specialized construction materials designed to enhance waterproofing or securely hold the connector boots in place. While this may not be a concern for riders who frequently encounter adverse weather conditions, it is something to consider when evaluating the overall durability and longevity of the spark plug wires.

Regrettably, the product description lacks specific information about the resistance of the materials used in the construction of these wires. While resistance is an essential characteristic in spark plug wires, its omission from the provided details leaves enthusiasts wanting more information regarding the performance and reliability of the product.

Each kit conveniently includes a set of two spark plug wires, ensuring riders have everything they need to complete the installation process seamlessly. The affordability of the kit is also worth noting, as it retails for an enticing price of approximately $29.59 USD, making it an accessible and cost-effective solution for Harley-Davidson riders seeking reliable spark plug wires.

In conclusion, this particular set of spark plug wires tailored for big twin 103 motors represents a fitting choice for Harley-Davidson enthusiasts seeking compatibility, customization, and ease of installation. While lacking some additional features found in alternative options, its competitive price point makes it an attractive option for riders who value affordability without compromising on quality.


Introducing the latest advancement in spark plug wire technology for Harley-Davidson enthusiasts, the Dragon Fire spark plug wires offer an unparalleled level of performance and durability. Building upon the success of its predecessors, these wires boast a remarkable combination of multi-layer insulation featuring Kevlar, fiberglass, and silicone.

However, the true innovation lies within the core materials of these upgraded spark plug wires. By incorporating an alloy conductor with a resistance of 150 ohms per foot, Dragon Fire has revolutionized the efficiency and reliability of the ignition system. This cutting-edge conductor material ensures optimal spark delivery, leading to improved combustion and enhanced overall performance.

Specifically designed to cater to the needs of Twin Cam 88 engines found in iconic models like the Heritage Softail and Fatboy motorcycles, these spark plug wires come pre-cut and crimped for a seamless installation experience. The precise measurements of 8″ and 20″ ensure a perfect fit and eliminate any guesswork during the setup process.

Priced at $44.95 USD for a set of two wires, the Dragon Fire spark plug wire replacement kit offers exceptional value for its advanced features. The slight increase in price compared to the previous options can be attributed to the incorporation of upgraded core materials and meticulous construction techniques. These enhancements guarantee unparalleled performance, durability, and longevity, making the investment worthwhile for passionate Harley-Davidson riders.

By opting for the Dragon Fire spark plug wires, Harley-Davidson enthusiasts can expect to experience a noticeable improvement in their motorcycle’s ignition system. With enhanced spark delivery, riders will witness smoother acceleration, increased power output, and improved fuel efficiency. Moreover, the durability of the wires ensures that they can withstand the rigors of demanding riding conditions, making them a reliable companion for long journeys and thrilling adventures.

As a true expert in the realm of Harley-Davidson motorcycles, it is my pleasure to recommend the Dragon Fire spark plug wires as the ultimate choice for riders seeking optimal performance and reliability. Embrace this technological marvel, and let your Harley-Davidson motorcycle roar to life like never before.


If you happen to own a Harley-Davidson motorcycle that specifically requires 8mm spark plug wires, you may find yourself reluctant to opt for the obvious choice of aftermarket red wires that seem to be a common sight. Luckily, a new replacement option has emerged, offering a more discreet and stylish alternative with its sleek black color. ACCEL, renowned for its high-quality motorcycle parts, introduces spark plug wires designed to meet the needs of Harley-Davidson Sportster engines manufactured between 1986 and 2006.

What sets these ACCEL spark plug wires apart is their superior construction. At the coil end, they feature brass terminals that enhance conductivity and ensure a reliable electrical connection. The wires themselves are fortified with a fiberglass braided cover, providing added durability and protection. To safeguard against external elements and ensure optimal performance, the wires are further encased in a thick outer silicone jacket.

In terms of compatibility, these 8mm spark plug wires are specifically tailored to suit the Sportster series, catering to the requirements of Harley-Davidson enthusiasts who are proud owners of these iconic machines. To guarantee a seamless fit and hassle-free installation, each replacement kit comes with two spark plug wires that are pre-measured according to the exact specifications of the Evolution motor, which powers the Sportster models.

It is important to note that the slightly smaller diameter of these wires translates into a higher resistance, which contributes to efficient electrical transfer and overall performance. With a rating of 500 ohms per foot, these ACCEL spark plug wires are engineered to optimize the ignition system of your motorcycle, providing reliable and consistent sparks for smooth engine operation.

In terms of peace of mind, ACCEL stands behind the quality of its product. Each replacement kit comes with a generous 90-day warranty, offering assurance and support to customers. Priced at approximately $35.35 USD, this replacement kit provides an affordable and worthwhile investment to enhance the performance and aesthetic appeal of your Harley-Davidson motorcycle.

With ACCEL’s black 8mm spark plug wires, you can now upgrade your Harley-Davidson Sportster with a discreet and stylish touch. Embrace the combination of functionality, durability, and aesthetics that these wires offer, allowing you to stand out from the crowd while ensuring optimal performance on the road.

Frequently Asked Questions

Frequently Asked Questions

When it comes to Harley-Davidson motorcycles, the options for spark plug wire replacements are diverse, ranging from various colors and brands to different thicknesses and materials. While some may argue that bigger is always better, it is crucial to understand the reasons behind the increased thickness and how it impacts your motorcycle’s performance.

Which is better for my Harley engine, 8mm or 10mm spark plug wires?

The advertised increase in diameter for different spark plug wires is primarily due to the thicker core, which serves as the conduit for electricity between the ignition coil and the spark plug. Smaller wires have a smaller diameter, resulting in a higher resistance path for voltage. Conversely, thicker wires feature a larger core diameter, offering a lower resistance path for electricity. This reduced resistance allows more power from the ignition coil to reach the spark plug. Most spark plug wire manufacturers specify resistance details in ohms per foot, helping you make an informed choice.

Do larger spark plug wires genuinely enhance engine performance?

While it is essential to consider any specific demands your engine may have regarding spark plug wire size, there is a compelling argument in favor of larger wires due to their lower resistance. The availability of increased voltage at the termination point of the spark plug wire means that if your engine is tuned or you’re using a power commander, you could potentially adjust the air/fuel ratio, requiring less fuel for optimal running and riding performance.

However, there are drawbacks to using larger-than-OEM spark plug wires. These larger wires can potentially introduce more electromagnetic frequency interference (EMI) or radio frequency interference (RFI). In stock applications, such as those with a stock ignition coil or magneto, the larger spark plug wires may not yield measurable power or efficiency benefits. For most stock and non-performance applications, it is recommended to use the standard-issue spark plug wire size to avoid any performance drawbacks. It’s worth noting that while most Harley-Davidson replacement spark plug wire kits come in 10mm, older engines like the Evo motor may require the use of smaller 8mm spark plug wires.

Lastly, the compatibility of larger spark plug wires with existing wire clips must be considered. If you decide to opt for significantly larger wires without checking their fitment, you might need to improvise a DIY clip or routing solution to keep everything in place. While it’s not a major compatibility issue, it’s something to keep in mind if you prefer a hassle-free installation experience.

What factors should I consider when researching or purchasing a spark plug wire replacement kit?

When researching or buying a spark plug wire replacement kit for your bike, it is crucial to prioritize fitment and compatibility. This applies especially to spark plug wire kits, as you need to consider not only the wire’s diameter and size but also the length of each wire and the type of connector boot it utilizes (straight or L-shaped). In automotive and motorsport applications, spark plug wires come in various lengths to accommodate the different distances between the coil and the cylinder. Some spark plug wire replacement kits come pre-measured, pre-cut, and pre-crimped with attached connector boots, eliminating the need for measuring and cutting the wires. With these convenient kits, you only need to ensure that the replacement wires are the correct length. However, not all kits on the market come pre-cut and crimped, so it’s important to verify the specifications before making a purchase decision.

In conclusion…

When it comes to finding the perfect set of spark plug wires for your beloved Harley-Davidson motorcycle, the process doesn’t have to be a daunting one. By understanding the impact of various factors such as size and construction on your bike’s performance and actively seeking out those specific details during your research, you can simplify the selection process. It is important to recognize that each spark plug wire available on the market is distinct, featuring diverse core materials, insulation layers, and types, each contributing to varying resistances based on the diameter and core material type.

Deepening your knowledge in this domain empowers you to differentiate between a potentially well-constructed budget option and a visually similar product that may not meet the same standards. As a true Harley-Davidson enthusiast, you understand the significance of quality craftsmanship and the importance of making an informed decision.

As always, when embarking on the journey of researching replacement parts online, it is crucial to verify the fitment and compatibility of any parts you are considering or searching for. In the case of spark plug wires, a useful approach is to familiarize yourself with the original equipment manufacturer (OEM) specifications regarding the length and diameter of the existing spark plug wires before initiating the search for suitable replacements. This pre-knowledge will enable you to eliminate options that are clearly too long or too short for your specific engine, ensuring a more efficient and effective selection process.

It is worth noting that in certain applications, bigger spark plug wire diameters do not necessarily equate to better performance. It is essential to understand the concept of resistance in ohms, as it allows for a meaningful comparison between two sets of spark plug wires, ultimately guiding you in determining which one truly offers the best value for your hard-earned money. By evaluating the resistance levels, you can make an educated decision, ensuring that the spark plug wires you choose are optimized for your motorcycle’s unique requirements.

As a passionate and knowledgeable Harley-Davidson enthusiast, taking the time to delve into the intricacies of spark plug wires will undoubtedly enhance your riding experience. By leveraging your expertise and understanding the nuances of these vital components, you can confidently select the perfect spark plug wires that harmonize with your motorcycle’s performance goals and aesthetic preferences. Remember, the right spark plug wires not only enhance your bike’s overall performance but also contribute to the enduring legacy and iconic spirit of the Harley-Davidson brand.

All Wired Up: What You Should Know About Spark Plug Wires in Your Harley-Davidson (+ 5 Replacement Kit Options)
All Wired Up: What You Should Know About Spark Plug Wires in Your Harley-Davidson (+ 5 Replacement Kit Options)

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