COMP Cams Camshaft Lobe Center Marking Tool Set is constructed of aluminum and is available in three sizes for all common lifter bore diameters. With this tool the user marks the cam lobe with a type of marking fluid, installs, the cam, and then places the tool in the lifter bore. next the cam will be turned over to mark a line around the cam lobe. The cam is then removed, the distance from the edge of the lobe is measured and finally, shims are changed to achieve the correct lobe to lifter alignment.