Saves range time and ammo; highly accurate laser system lets you zero your scope to point-of-aim at 100 yards, before you go to the range. Quick and easy to use, just place the special laser target 25 feet away and aim the laser at it, then adjust the scope till the crosshairs align with the target. Works equally well with red dot scopes and iron sights. Laser is mounted to a cone shaped, aluminum spud. An O-ring and a powerful magnet hold the spud centered in the bore. No special adapters to buy and no metal contacts the rifling. A system of adapters and O-rings lets one unit fit all firearms from .22 to .50 caliber, plus 12 and 20 gauge shotguns. Also includes the SRL-100 adapter that slips over the Boresighter's lens to convert it into a highly accurate Scope Reticle Leveler by refocusing the laser to a horizontal beam for precise crosshair alignment. SRL-100 also available separately. SL-100 Standard Model for use indoors, where you have control over ambient lighting. SL-150 Ultra-Mag has an ultra-bright 635mm laser for better visibility in bright, ambient light conditions. SL-500 Ultra-Mag uses a super-bright green laser for maximum visibility of the sighting dot in daylight and very bright ambient light.