Gomadic Portable AA Battery Pack designed for the Microsoft Zune HD - Powered by 4 X AA Batteries to provide Emergency charge. Built using TipExchange Technology Built using the unique Gomadic TipExchange Technology that protects your investment by providing the ability to upgrade charging ports by simply swapping physical connectors. Specification: Input Voltage (4 X AA Batteries), Cable length (6 inches), Dimensions (5.0 X 1.5 X 0.75 inches), Circuit Design (Microsoft Zune HD specific), TipExchange enabled (Yes) Integrated circuitry regulates output voltage specific to the Microsoft Zune HD. Advanced logic maximizes overall charger efficiency. Easy to operate. Simply insert batteries, toggle on/off switch and your Microsoft Zune HD will start to charge. Internal circuit designed to protect your Microsoft Zune HD from power surges, overcharging and short circuiting.