Chamber the Sightmark(R) 300BLK (7.62x35mm) Boresight in your rifle like a regular cartridge, and a red laser dot shows exactly where you're aiming. Ideal for hunters, competitive shooters and law enforcement, this device significantly reduces wasted cartridges and shells. Simply adjust your sights or scope, and save your extra ammo for the hunt. Includes a carrying case, three (3) AG3 batteries, and instructions.