SET OF 2 PERFORMANCE SPARK PLUG Harley Davidson FXSTB Softail Night Train EFI 2008-2007 GFRT789BR14ZCYU878 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