American made tappets for Panhead, Shovelhead and Evolution engines 1953 to present. Made from aircraft quality steel, precision machined, heat treated and ground to less .0002" total indicator readings at a 16 finish. Inside the tappet is a hydraulic cylinder which is also hardened and hand fit to .0002" using air gauge. The tappet has a hardened pushrod seat. The inner valve is super flat and is helped by an internal spring to help hydraulic control. The Big Axle tappets are strongly recommended when using High Lift Performance cams. With Power Glide tappets Full power means zero valve lash, and zero hydraulic collapse. Power Glide tappets eliminate the shock absorber action and are capable of the highest RPM a Harley-Davidson can safely turn with the right equipment. Sold each.