COMP Cams offers two styles of Cam checking fixtures--heads on and heads off--to suit your automotive needs. The cylinder heads' off-engine fixtures were designed to maintain proper geometry, while holding a dial indicator (not included) and a 5 in. extension (included) precisely over the lifters. These professional quality tools are much easier to use and more precise than using a magnetic indicator base when degreeing a cam. These multi-functional tools can also be used to check Rocker ratio, piston to valve clearance, and even crankshaft end play.