BXT&reg; 2000mah For iPhone 4 / 4s External Rechargeable Spare Backup Extended Battery Charger Case Cover for Apple iPhone 4 / 4s Extended power pack for your iPhone ,available charging Anywhere at anytime! (new product on sell for iPhone 5/5s/5c http://www.amazon.com/gp/product/B00NHI10N8) 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 210 hrs for iPhone 4/4s;talk time up to 8hrs;Audio playback 28hrs Capacity:2000mAh;Size:13*6.5*2 cm; Weight:75g;Material quality :general-purpose plastics ;Build in battery:Grade A lithium battery