General Spec Color white Capacity 1600mAh, 3.7V/4.2V Input 5.0V Output 5.0V Charging Time 4.5hours Compatibility iPhone 4 Features Hight quality, elegant and stylish. Designed to fit the contour of iPhone 4 precisely. Ultra slim and custom-fit with open-face design for easy operation. Can extend standby time effectively and provide sufficient power to your phone at any time. The battery inside the case can transfer 85% power to your phoone to realize charging and using the phone simultaneously. The button on the case is designed to be customized which allowes you to choose when to use. Can protect your phone from scratching and dirt. Easy access to all buttons, controls and ports without removing the shell.