The Sightmark Triple Duty Universal Green Laser Boresight is a compact, lightweight and most accurate Universal Borsight on the market. Field tested and approved by the North American Hunting Club, the Boresight works on all .17-.50 caliber rifles, shotguns and pistols. Engineered with a self-centering arbor, the Sightmark Triple Duty Universal Green Laser Boresight 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. One (1) CR2 battery, a carrying case and instructions are included.