Unique Gomadic Portable Rechargeable Battery Pack designed for the Zoom H4n - High Capacity Gomadic charger that fits in your pocket Very easy to operate. Simply connect Zoom H4n, press activation button on pack, and charging begins. Quick start guide included. Specification: Internal Battery (7800mAh lithium polymer), Input port (microUSB), Output Port (Standard USB), Onboard Circuit Design (Zoom H4n Specific), Dimensions (2.75 X 3.25 X 0.75 inches), TipExchange enabled (Yes) Integrated circuitry tailors output voltage and charging current to exact specification of the Zoom H4n (accurate to 0.1v). Built with high capacity lithium polymer rechargeable battery technology (28 Wh / 7800 mAh) in a compact design. Built using unique Gomadic TipExchange Technology that protects your investment by providing the ability to upgrade charging ports by simply swapping the physical connector.