This universal set of 8.8 mm spark plug wires is constructed with silicone throughout the jacket, insulation and core to deliver high-temperature resistance. Made to hold up to the harshest conditions, rated at SAE Class E J2031 with a continuous operating temperature of 450 F. NOTE: This kit WILL NOT work on Twin Cam model Harley Davidsons.The plug wire measures 39 1/2″ long including the spark plug boots. Made in the U.S.A.