This hassle-free boresighting system fits in the chamber of your rifle or pistol and projects a powerful red laser beam aligned with the bore axis for sighting to the point-of-aim without firing a shot. Works with scopes, holographic red dot sights, and variety sights. Durable, machined brass housing looks like a cartridge case but actually contains the entire laser system and batteries. Insert the batteries and screw the cap on the housing to turn on the laser; remove the batteries to turn off. Insert the entire assembly into the chamber, gently close the action, and aim at a target 20-30 yards away. Adjust windage and elevation of the scope or sights so point-of-aim is zeroed on.