From the manufacturer:
The powerful and versatile SureFire X300 Ultra WeaponLight for handguns and long guns features a high-performance LED that generates 600 lumens of stunning white light focused by a Total Internal Reflection (TIR) lens to produce a tight beam with extended reach and significant surround light for peripheral vision. The virtually indestructible and highly efficient LED generates tactical-level light—more than enough to overwhelm an aggressor's dark-adapted vision—for 1.5 hours per set of batteries.
Activating the X300 Ultra is done via ambidextrous switching located at the rear of body, providing one-finger control — press the switch on either side for momentary-on activation, flip up or down for constant-on activation. Optional DG grip switches (for pistols) and a pressure activated XT07 tape switch (for long guns) permit the X300 Ultra to be activated without altering your grip on your weapon.
The X300 Ultra can be attached to a pistol or a long gun since its Rail-Lock® system permits rapid attachment to and removal from either Universal or Picatinny rails. Its high-strength aerospace aluminum body is Mil-Spec hard anodized for superior toughness and is O-ring and gasket sealed to make it weatherproof.
FITS: Handguns and long guns with Picatinny or Universal rails. Adapter mounts available for several non-railed handguns