MiPow Power Tube 3000 mAh Backup Battery for Cell Phones, MP3 and Tablets - Grey Apple iPhone 4S/Apple iPhone 4/Apple iPhone 3GS/Apple iPod/other mobile devices which support 5V/1A input (by USB cable) Compact in size for easy transport Lithium Polymer, 5 Volt, 1 A Cycle Life: 500 times DC Charging