Retro-fit lifter for blocks originally equipped w/ flat tappet cams; Tall body fits both standard blocks & tall lifter bore aftermarket/OEM blocks. Precise piston fit for lowest leakdown rate; Patent-pending piston allows trapped air to escape lifter for faster pump up. Axles produced from premium 52100 heat-treated steel for increased wear resistance & overall strength; Lightweight body design; Includes (2) lifters;