Tursion High Quality 1600 mAh External Battery Pack Portable Power Bank Case Charger with FM Transmitter for Apple iPhone 4S 4 - AT&T and Verizon Simply charge this iPhone Case Charger from your PC using the provided USB Cable until it is full; then simply charge your device whenever you need power. Rechargeable Lithium-Ion 1600mah battery pack increases energy efficiency. Great for traveling and long flight for your iPhone 4 and 4S. Built in FM Transmitter to broadcasto to radio devices Compact size allow easily carry in bags, pant pockets, or shirt pocket 4 LED battery meter displays remaining power level.