The Nitecore NL1826R is button top rechargeable 18650 Li-ion battery. The dual-LED power indicator located next to its positive terminal, which glows red while charging and green once charging is complete. The battery has 3.7V with 2600mAh of capacity. Built-in smart micro-USB port for easy charging. The NL1826R Li-ion batteries are designed for powering high drain devices such as flashlights, lanterns, headlamps, and bike lights, as well as various other devices.