The Fenix TK (Tank) series features a powerful, solid, durable, and waterproof design intended for rugged outdoor and military use. The TK11 uses one 18650 Li-ion or two CR123Abatteries and maintains excellent constant brightness with two output modes: General mode, which can last for a whole night and can be used for general illumination, and Turbo mode, which can be used whenever high-powered light is needed – search and rescue, long-range target identification, etc.