Energizer Energi to Go Portable Case Charger for AT&T and Verizon iPhone 4 (Black) Flexible form-fitting silicone rubber case with built-in rechargeable battery; made for iPhone 4 Integrated bumper eliminates prevents signal loss or antennae interference caused by direct contact Simultaneous pass through charge to your iPhone 4 and the case Flexible form-fitting silicone rubber case with built-in rechargeable battery; made for iPhone 4 Integrated bumper eliminates prevents signal loss or antennae interference caused by direct contact Simultaneous pass through charge to your iPhone 4 and the case Extra thin and easy to handle; durable, nonslip material Provides up to 5 hours of 3G talk time, 7 hours of video playback, and 27 hours of music playback (in addition to iPhone's battery)