hsini 1900 mAh External Backup Charger Battery Case for Apple iPhone 4 4G & 4S - Retail Packaging - Blue Compatible Device: Apple iPhone 4S /4 High-capacity,1900mAh rechargeable lithium-ion battery/ Output 5V/500mAh Fully charged in 3-4 hours, 4 Led lights indicates the power level Light-weight, super-slim design to carry with your iPhone as well in style