The ARB-L18-3500U is a high-capacity 18650 Li-ion USB rechargeable battery featuring a built-in micro-USB charging port. Equipped with a protection circuit in the anode, it effectively prevents short circuits, overcharge/discharge, and overheating. These USB rechargeable batteries can be rapidly charged without the need for a separate charger, saving you money and eliminating the hassle of carrying an additional device. Compatible with all current models utilizing a li-ion 18650 battery, this battery ensures convenience and reliability. Please note that a micro-USB charging cord is NOT included.