Featuring two levels of tactical illumination, ambidextrous switching, a slender ergonomic design, and legendary SureFire reliability and durability, the DSF-500/590 is the ultimate WeaponLight for Mossberg 500 or 590 shotguns. This compact, lightweight system replaces the weapon?s original factory forend and features a recoil-proof LED that generates 600 lumens of blinding white light at maximum output, or 200 lumens with twice the runtime on its high setting. The LED?s light is focused by a precision reflector to create a smooth, wide beam perfect for closer-range shotgun applications typical in law enforcement and home defense-with enough reach and surround light to properly identify threats and maintain situational awareness. The DSF-500/590 features large, tactile momentary and constant-on switches on both sides for precise control by left- and right-handed shooters. Selecting the LED?s output is achieved by activating the light in constant-on mode and then pressing the output-mode selector switch until the desired output level (600 or 200 lumens) is set. The selected output can then be left in constant-on mode or switched to momentary activation, and it stays at that output level until reset. Every DSF-Series WeaponLight also features an integrated system-disable switch to prevent accidental activation during transport, storage, or stealth operations. A lightweight but strong aluminum module protects the optics, LED, and sophisticated electronics, minimizing length with side-by-side placement of the two lithium batteries that power the system. The module has a Mil-Spec hard anodized finish to protect against scratches, abrasion, and corrosion, while O-ring and gasket seals keep out moisture, dust, and debris. The slender forend body is made from extremely tough polymer and is textured for a secure hold and features large, tactile momentary and constant-on switching on both sides for precise control by left- and right-handed shooters. The DSF-500/590 fits as-is any 500 or 590 shotgun variant with a 6 3/4" forend tube (magazine tube). An included internal spacer provides a proper fit for 7 3/4" forend tubes..