This Nextorch 18650 lithium-ion battery has a 3,400 mAh capacity and charges directly through a USB port built into the cell, so you do not need a separate battery charger; a charging cable is included. It suits flashlights, headlamps and other devices that take an 18650 cell. Nextorch's current 3,400 mAh 18650 cell is rated 3.6 V and 12.24 Wh, is good for more than 500 charge cycles, and has protection against overcharge, over-discharge, over-current and over-temperature. It weighs about 57 g and measures about 18.8 mm across by 70 mm long; protected USB cells are slightly longer than plain 18650s, so check that it fits your light. Operating temperature is about -20 to 60 °C.