HP stands for high-powered. The TLR-1 HP series produce a long-range targeting beam that reaches 400 meters! C4 LED technology, impervious to shock with a 50,000 hour lifetime 46,000 candela peak beam intensity 200 lumens runs 1.75 hours Mounts directly to all MIL-STD-1913 Picatinny rails and weapons with Glock-style rails Includes rail locating keys for mounting to a variety of rails and lithium batteries Standard door switch Standard Switch Ambidextrous momentary/steady On-Off Tethered battery door and latch mechanism prevents battery door loss while providing easy battery replacement One handed snap-on and tighten interface keeps hands away from muzzle when attaching/detaching Extensively live-fire tested impact resistant construction Deep dish parabolic reflector produces long-range targeting beam with optimum peripheral illumination Powered by two 3V CR123A lithium batteries included Durable anodized aluminum construction Unbreakable polycarbon Streamlight TLR-1s HP White LED TLR-1 HPL Std; Lithi Batt. White LED