Crimson Trace Corporation Rail Master Tactical Light, Fits 1913 Picatinny Rail, High Beam, Low Beam, Strobe, And Momentary Modes, 1 Hour 50 Min Runtime at 110 Lumen, 1 Hour 5 Min Runtime at 420 Lumen on one CR123 Battery, Anodized Aluminum, Waterproof Up to 1 Meter, Black Finish 01-8240-1