BaoCore BXT&reg; iphone 4 / 4s External Rechargeable Spare Backup Extended 2200 mAh Battery Charger Pack Case Cover for Apple iphone 4s Black Extended power pack for your iPhone ,available charging when walking ,having class,on work,on the subway,in car.Anywhere at anytime! Easy using,slide your iphone 4/4S to the bottom,place the roof cover back and it's all right now.Turn it ON when charging. Be convenient,you can just keep it in hand .Easy carrying with and offer extra full protect to your iPhone Extend standby time up to 215 hrs for iPhone 4/4s;talk time up to 8.5hrs;Audio play 25hrs Capacity:2200mAh;Size:13*6.5*2 cm; Weight:75g;Material quality :general-purpose plastics ;Build in battery:Grade A lithium battery