Ultimate Arms Gear .45 Caliber Internal Interbore Pistol Revolver Handgun Chamber Barrel Bore Borelock Muzzle Security Safety Key Lock for .45 ACP, .45 Long Colt, .45 Winchester Magnum Fits 2 3/4" - 4 1/4" Revolver Barrel Length & 3 3/4" - 5 1/4" Auto Pistol Barrel Length