Spark Plug Copper Spark Plug Copper Spark Plug; Motorcycle Spark Plug; Harley Twin Cam; .040 in. Gap; 2 Pack ; SPECIFICATIONS: WARNING CA Proposition 65: Yes FEATURES: U-Groove Ground Electrode Heavy-Duty 5 Rib Insulator Copper/Nickel Alloy Conductor Highest Performance On The Market ACCEL U-Groove performance spark plugs have a patented U-shaped ground electrode that produces a double wide, hotter spark to ignite standard or even the highest compression engines. The sintered alumina heavy-duty five rib insulator eliminates flashover and overheating that occurs with high performance and long range applications. ACCEL U-Groove spark plugs use the purest copper/nickel alloy electrode to produce a broad heat range that is highly foul resistant and dissipates heat better than any other material. Years of racing and street performance research has proven that ACCEL U-Groove spark plugs deliver the hottest spark and the highest performance of any spark plug available. For more than 40 years, ACCEL has been a leader in performance fuel and ignition systems, proving itself on the racetracks and drag strips of the world - and on the street. With an ever-expanding line of SuperCoils and all the spark plug wires, tune-up kits, and fuel injectors hot rodders have trusted and relied on for years, ACCEL is constantly developing innovative new products designed to push power, speed, and performance to match advancements in automotive technology. Now part of Holley Performance, ACCEL offers a comprehensive selection of performance products, including coils, digital fuel injection systems, fuel injectors, distributors, caps, rotors, ignition wires, spark plugs.