The juice pack airâ„¢ is a rechargeable external battery concealed inside of a protective form-fitting—case for the iPhone 3G & iPhone 3GS. It offers you the full protection of a hard-shell case while providing—virtually twice the battery life of the iPhone alone; all in an ultra-thin light-weight low-profile design.——The juice pack airâ„¢ is specially designed for iPhone 3G & 3GS and has passed the strict over-the-air—performance tests by an Apple designated test lab. As a result the mophie juice pack airâ„¢ has been officially certified by Apple Inc. as a “Works with iPhone 3G(S)â€� product!