This innovative tool slides into the lifter bore and rides on the Camshaft to measure lobe lift and base circle runout. The tool includes two followers: one for Solid and hydraulic flat tappet cams and one for Roller cams. Built-in o-ring holds tool firmly in the lifter bore while a 1" travel dial indicator (not included) reads Cam lift to .001". Fits GM (.842" dia.) and Ford (.875" dia.) lifter bores.