Ultimate Arms Gear .22 Caliber Internal Interbore Pistol Revolver Handgun Chamber Barrel Bore Borelock Muzzle Security Safety Key Lock for .22LR .22 Long Rifle Fits 3 1/4 " - 4 3/4" Revolver Barrel Length & 4 1/4" - 5 3/4" Auto Pistol Barrel Length