HP stands for high-powered. The TLR-1 HP series produce a long-range targeting beam that reaches 400+ meters! C4A(R) 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. Available with either standard door switch or remote door switch. Standard Switch: Ambidextrous momentary/steady On-Off. Remote Switch: Momentary/steady On-Off and port plug for remote switch assembly 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 polycarbonate lens with scratch-resistant coating IPX7 rated design; waterproof to 1 meter for 30 minutes Operating temperature: -40AdegF to +120AdegF Serialized for positive identification Length with standard switch: 4.83 in. (12.27 cm) Length with remote switch: 5.25 in (13.34 cm) 5.3 oz (150.3 grams) with standard switch and batteries 5.6 oz (158.8 grams) with remote switch and batteries Limited lifetime warranty