The Fenix TK35 is a convenient and extremely high intensity multi-function flashlight. Featuring up to 860 lumen output, the TK35 offers four brightness levels, two different flashing functions, and a signaling mode. It is powered by CR123A lithium batteries or high capacity 18650 rechargeable Li-Ion batteries. The unique design of the battery holder not only makes the light more compact but makes it more comfortable to hold and easier to use. With its dual button switch, you can change brightness levels rapidly. Other features include: Cree XM-L (U2) LED with a lifespan of 50,000 hours Uses four 3V CR123A batteries (Lithium) or two 18650 rechargeable batteries (Li-ion) 164mm (Length) x 43.64mm (Diameter) x 51.5mm (Head) 256-gram weight (excluding batteries) Digitally regulated output - maintains constant brightness Reverse polarity protection, to protect from improper battery installation Dual button switch in the tail cap, convenient operation Made of durable aircraft-grade aluminum Premium Type III hard-anodized anti-abrasive finish Toughened ultra-clear glass lens with anti-reflective coating ANSI/NEMA FL 1 Ratings: --Turbo: 860 lumens (1 hour 37 minutes) --High: 365 lumens (6 hours 48 minutes) --MID: 120 lumens (23 hours) --Low: 15 lumens (130 hours) --Flashing: 860 lumens --SOS: 120 lumens TK35 will automatically change the turbo brightness level to the high brightness level after a 25-minute working time with the security setting. So the runtime of the turbo brightness level is the accumulated time.