The Redding Case Neck Gauge Pilot Stop is designed to work with the Redding Case Neck Gauge to allow reloaders to precisely measure different caliber cases. The unique, undercut shape will not pick up imperfections in the case mouth or neck/shoulder junction ensuring extremely accurate readings on the dial indicator. Notes: Pilot stops from 17 caliber to 243 caliber are available for the 9/64" mandrel, while pilot stops for the 3/16" mandrel are available from 22 caliber to 338 caliber