Site Lite® SL-100 Laser Boresighting System has the latest laser technology to provide superior boresighting accuracy. Super-strong magnets in the arbor securely centers the laser within the muzzle for consistent accuracy. A unique system of adapters and O-rings fit .22 to .50 cal., 20 gauge and 12 gauge shotguns, plus muzzleloaders. No metal contacts the rifling. No optional arbors needed!