The SL-100 Mag Laser Boresighter combines the latest laser technology with magnetic to provide superior boresighting accuracy! This unique system uses a combination of adapters and o-rings to fit all firearms, including .22 to .50 caliber handguns, .22 to .50 caliber Rifles, 20Ga. & 12Ga. Shotguns and Muzzleloader! There are no optional adapters to buy and no metal contacts the rifling. The SL-100 is precision machined, aircraft quality, anodized aluminum. A system of super strength magnets, within the center cone, securely holds the SL-100 in the muzzle to insure repeatable, superior accuracy. To boresight, place the target 25 feet from the muzzle and center the laser spot on the target. Then, line up the scope crosshairs with dotted lines on the target and you're boresighted for 100 yards. It's that simple!