No more fumbling with a magnetic base and a dial indicator to measure cam lift. This fixture maintains and holds the dial indicator and 5in extension (included) in the precisely correct position over the lifters, assuring proper geometry. Supplied with 1/2in and 7/16in adapters for use with any engine block. (with cylinder head off) Includes 0-1.000in Dial Indicator 66962 (0.001in)