Cut your sight-in time. The X-Ring Boresighter will begin the sight-in process before firing a shot. The laser dot helps a shooter to align the scope or sights with the barrel. This makes the whole sight-in more efficient. Save time and ammunition. Features a positive on / off switch to improve battery life. Allen provides all the fittings you need to make your laser boresighter adapt to almost any gun, sized to fit .177 to .50 caliber rifles, or 12 and 20-gauge shotguns. The Allen Company X-Ring Laser Boresighter value pack includes a battery and mounting screws for easy assembly.