S&S Cycle specifically developed the bolt-in 557 Easy Start cams for the HD Tri Glide models. Bolt-in - no headwork Super torque cam to accelerate the extra weight of a Trike The short duration produces lots of torque, and the automatic mechanical compression release makes the engine a snap to start Start any engine with a stock starter Save your starter and battery Reliable - tested for 100,000 accumulative starts and over 150,000 road miles without breakage or compression release failure Automatic - no buttons to push