The CMR-201 Rail Master is a powerful and versatile laser sight designed to fit rail-equipped pistols, rifles and shotguns. The Rail Master locks onto Picatinny M1913 or Weaver-style accessory rails with Crimson Trace's Secure-Lock Technology. Once locked on, it will not move under recoil or handling. The universal design of the Rail Master offers quick Instant Activation by simply "tapping on" and "tapping off" from either side with the ambidextrous activation control tabs. Wrench Size - 0.05..