Field tested and approved by the North American Hunting Club,the Sightmark Universal Boresight is a compact and lightweight device with a red laser for sighting in rifles, pistols and shotguns .17 – 50 Cal. The reliable and durable boresight reduces wasted cartridges and shells. Simply place the base of the boresight onto the end of the barrel of your weapon and it will attach magnetically. A battery pack ( three (3) AG3 batteries) and a carrying case are included.