1900 mAh External Backup Charger Battery Case for Apple iPhone 4 4G & 4S -Black Designed to provide power for your iPhone 4/4S Compact and lightweight, you can use your iPhone as usual as you use this external battery Built-in 1900mAh high capacity rechargeable Li-Ion battery Can also work as a protective case, 4 LED power indicator Battery itself charged through USB port or USB charging adapter