ARB-L21-5000U is a high capacity 21700 Li-ion USB rechargeable battery built for more power and longer runtimes. This battery has its own USB-C charging port for quick/easy charging without the need for a separate charger. Additional features include a protection circuit in the anode to help prevent short circuits, over charge/discharge and over heating. Pressure relief vents which expel waste gas in the rare case of an internal short circuit preventing an explosion. Battery capacity up to 5000mAh. 500 charging cycles. This product will only work in those models supporting 21700 batteries. A USB-C charging cord is NOT included. Important Note: THIS BATTERY IS NOT COMPATIBLE WITH 18650 FLASHLIGHTS OR OLDER STYLE CHARGERS.