iPhone 4 4S USB Ultra Slim Portable 3200mAh Battery Charging Case Rechargeable Backup Powerr Bank Supply For iPhone 4 4S(IOS 7) AT&T, T-Mobile, Verizon, Sprint 3200mAh Backup Power Extender Charger Case for iPhone 4 4S Compact and lightweight, you can use your iPhone as usual as you use this external battery Built-in 3200mAh high capacity rechargeable Li-Ion battery Can also work as a protective case, 4 LED power indicator Keep Battery Case charge via USB Port