Boostpac Auxiliary Battery Pack for your iPhone built into an ergonomic, slimline easy-grip case doubling your iPhone battery power! Standby time - up to 270 hours for 3G, up to 300 hours for 3GS. Music time - up to 20 hours for 3G, up to 27 hours for 3GS. Talk time - up to 4.5 hours for 3G, up to 4.5 hours for 3GS. Video time - up to 6 hours for 3G, up to 9 hours for 3GS, Internet time - up to 4.5hours for 3G, up to 8 hours for Wi-Fi. “Works with iPhone” means that an electronic accessory has been designed to connect specifically to iPhone and has been certified by Apple.