CenterPoint Laser Boresighter Rated to 100 yards of visibility at night, 25 yards in daylight Fits .177 caliber to .50 caliber rifle / pistol and 12, 16 and 20 gauge shotguns Requires minimum 3.8" long barrel Please refer user manual attached below for instructions and troubleshooting steps. Class IIIR Laser; less than 5mw