The ARB-L18-2600 is a high capacity 18650 Li-ion rechargeable with a protection circuit in the anode to help prevent short circuits, over charge/discharge and over heating.The battery also includes pressure relief vents.
The ARB-L18-2600U is a high capacity 18650 Li-ion 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. (Charging Current USB Port: 1A)