"The gauge allows you to see just how much you are sizing back."one piece gauge that will check overall length to indicate the need for trimming,datum to head length to assure correct headspace and to prevent oversizing.Available for most popular rimless cases.Note: Does not measure body diameters.This gauge is intended to be used with fired casesto determine a basis for full length sizing and trimming.L.E. Wilson has been making precision reloading tools for over 80 years. The Case Length Headspace Gauge allows reloaders to measure case length from the base of the cartridge to the shoulder, as well as the maximum case length. This process shows the reloader if ammunition is being produced within specifications.Technical InformationMaterial:SteelFeatures:Precision MachiningNotes:This is