SET OF 2 PERFORMANCE SPARK PLUG Harley Davidson FX Shovel Head 1984-1975 * GFRT734BR10ZCYU823 1. Higher HP and torque by up to 3 % 2. increased economy by up to 5% 3. 360 Firing Technology 4. Improved acceleration by up to 15 % 5. 25,000 miles - 40,000 km duration