The Sightmark Professional Universal Green Laser Boresight is designed for sighting in .17-.50 caliber rifles, shotguns and pistols. The unit provides the fastest gun zeroing and sighting system to reduce wasted cartridges and shells when sighting in your new optic. Its durable, ultra-compact design makes it easy to pack for travel, and includes an ultra strong magnetic base that is expanded to fit shotguns and muzzle brakes. The boresight features digital on/off and mode controls and long lasting battery life using CR123A batteries.