Upgrade the spark and throttle response on your Evo and early Twin Cam Sportster and FL models with the Sumax 409 Pro Race Spark Plug Wire Kit. Built around a 10.4 mm Spiro-Pro core, these wires deliver up to 10× the conductivity of standard carbon-core wires, running cooler, lasting longer, and keeping your Harley firing clean. Each pair comes precut with terminals and boots already installed, wrapped in high-temp silicone insulation rated to 600°F for serious durability. Made in the USA and ready to drop in — no trimming, no hassle.