These are the ULTIMATE flat tappet lifter. They are the same M1 tool steel USA made polished lifter as the other we sell but are DLC coated. The DLC is a low friction coating that allows the lifter to be ran on about any style flat tappet cam made. They will work with all hardface overlay cams and all heat treated tool steel flat tappet cams. These will be the very end to all your flat tapped cam problems. You can run these with as much spring pressure as you want and as many rpm as you want too. They work with the horizontal and vertical Command engines. They are sold EACH so if you need a set of 4 then add 4 to your cart.