Simply drop a loaded round into the precision made gauge and if your cartridge fits the gauge it'll fit your pistol. Gauge checks both chambering as well as cartridge length. - Quickly confirms ammunition will fit your pistol's chamber - Easy-to-read engravings display caliber size - The RCBS Chamber / Cartridge Gauge is a one-piece non-adjustable gauge designed to check all critical dimensions of pistol ammunition to insure proper fit.