This is a Streamlight Tac Light Kit known as the TLR-1 HPL, model 69219.
Long range" high lumen lithium battery powered Gun-Mounted Tactical Light featuring the latest in shock-proof power LED technology and providing 1.75 hours of run time. Tethered battery door and latch mechanism prevents battery door loss while providing easy battery replacement. Rail clamp designed to rapidly attach/detach from side of weapon. When enabled" strobe activated on two or more momentary paddle hits.
Features:
Powered by two CR123A batteries
IPX7 waterproof
C4 LED technology
Fits broad range of weapons
Strobe mode can be enabled/disabled
