The Sinclair Bullet Seating Depth Tool has been used for decades by handloaders seeking the most accuracy out of their rifles. Our newest model is made from one fourth inch ground and polished stainless steel with one end turned down for use with 17 and 20 caliber rifles and the other end used for 22 caliber and up. This tool helps you determine the length of a loaded round touching the rifling. The Sinclair Seating Depth Tool will work with most bolt action, single shot and AR type rifles. The tool includes a Delrin action guide suitable for most bolt-action rifles (0.690" Diameter fits Remingtons, Savages, Winchesters, and many Rugers). For the most accurate measurement, the S Mfg: Sinclair International