These ACCEL copper spark plugs fit Harley Davidson Twin Cam engines with .40" gap.

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 99-17 Twin Cam and 86-20 XL