The Gerber Cortex Flashlight is a bright, dependable everyday tactical carry light. Adaptable with dual power source and multiple modes. The Cortex Flashlight runs on either 3 Lithium CR123 batteries or 2 AA batteries, allowing you to use whichever power source is desired. When powered by the CR123s, it provides 675 lumens of output... enough to overwhelm an aggressor or identify a threat. It also has a strobe mode for tactical applications and a low-output mode for administrative duties.Take a look:Black anodized aluminum body High, low and strobe modes Waterproof (IPX7) Pocket clip Tailcap switch Lithium CR123 battery performance: 675 lumens for 1.75 hours 30 lumens for 40 hours AA alkaline battery performance: 390 lumens for 1 hour 28 lumens for 15 hours Overall length: 6 1/8 weighs 5 ozs. Lifetime warranty.