ARB-L18-3500U is a high capacity 18650 Li-ion USB rechargeable battery with a built-in micro-USB charging port. It also includes a protection circuit in the anode to help prevent short circuits, over charge/discharge and over heating. These USB rechargeable batteries can quickly be charged without the need for a separate charger. This not only saves you money from purchasing a charger, but also provides the convenience of not having to carry around another device. This will work in all of the current models that utilize a li-ion 18650 battery, including best sellers like the PD35 V2.0, PD35TAC, TK20R, TK75, TK15UE, and more. A micro-USB charging cord is NOT included.