ARB-L21-5000U USB rechargeable 21700 Li-ion battery, sufficient power, steady performance, the capacity of the 21700 battery is twice as powerful as the common 18650/2300mAh battery. Which provides the lighting tools with sufficient power and longer duration. Multiple protection, ensure the use of safety and good performance of the battery; Steel shell riveting technology, fully protected the battery against damage; Pressure relief vents, rapidly expel internal gas.