The Triple Duty Universal Green Laser Boresight is designed for sighting in .17-.50 caliber rifles, shotguns and pistols. A key feature of the device is it doesn't 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 then sight in at 25 yards. Includes a carrying case, one (1) CR2 battery, and instructions.