Tested and recommended by the National Tactical Officers Association and the North American Hunting Club, the Triple Duty Universal Red Laser Boresight is designed for sighting in .17-.50 caliber rifles, shotguns and pistols. A key feature to this device is it doesnt have any additional attachment pieces to be lost. Engineered with a self-centering arbor, the unit attaches into the end of the barrel as opposed to the inside, preventing metal from protruding into the firearm barrel. Simply place the base of the bore sight onto the end of the barrel, and it will attach magnetically. Includes a carrying case, three (3) AG13 batteries, and instructions.