Keystone ECO Holster Rechargeable Battery Case for iPhone 3G/3GS - Holster - Retail Packaging - White 1300 mAh Li-Polymer battery doubles available power Ergonomically designed Quick-Draw mechanism rapidly and conveniently presents phone to user Designed specifically as a reserve power supply for iPhone 3GS an iPhone 3G Automatically replenishes / tops-off charge of the iPhone when it is in the holster