This is a used Surefire 623FA Shotgun Forend WeaponLight.
Designed for Mossberg 500 and 590 Shotguns, this WeaponLight features an integral shock-isolated lamp assembly with a pressure sensitive momentary-on switch and an integral constant-on switch. The battery is prevented from slamming into the lamp assembly by a machined protective barrier for added resistance to the harmful effects of recoil. The batteries themselves are separated by a fiber washer and contained in a plastic sleeve as further insurance against recoil-related failure.
The 623FA WeaponLight replaces your standard factory installed hand guard. The lamp assembly produces a brilliant 65 lumen tactical-level beam that can run continuously for 60 minutes on two lithium batteries.
This 623FA is a versatile WeaponLight system that offers the operator several options to meet mission-critical requirements. The optional high-output P61 lamp can be installed for an outstanding 120 lumen beam, or the lamp head can be swapped out with an IR or visible laser module. The bezel measures 1.36", and it accepts accessory filters and a protective cover.