Portable Emergency AA Battery Charger Extender suitable for the Sandisk Sansa Express - with Gomadic Brand TipExchange Technology Integrated circuitry regulates output voltage specific to the Sandisk Sansa Express. Advanced logic maximizes overall charger efficiency. 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 (Sandisk Sansa Express specific), TipExchange enabled (Yes) A must have accessory for the frequent traveler, camper or heavy Sandisk Sansa Express user. Safely engineered with reverse polarity protection, in the event batteries are accidentally put in incorrectly.