The Comp Cams Hi-Tech pushrod length checking tools are precision crafted from steel alloy and black oxide for years of accurate measurements. The unique design is easy to read and eliminates the need for expensive calipers. Each complete revolution is equal to .050''. Having the correct length pushrods in your engine is a critical factor in proper rocker arm geometry and this is the best tool to measure pushrod length. It reads like a micrometer.