Bao Xin Colorful iPhone 4 4s Charger Case the Best iPhone External Battery Pack Protect Your iPhone All Around (Gray) High Quality and Finest Advance 2000mAh Lithium Polymer Back up battery for iPhone 4/4S Extend standby time up to 210 hrs for iPhone 4/4s;talk time up to 8hrs;Audio playback 28hrs Size:13*6.5*2 cm; Weight:75g;Material quality :general-purpose plastics ;Build in battery:Grade A lithium battery Best iphone 4 case .This backup battery pack charge your iPhone 4 wheneven you want ,also it's a protective case which protect your iPhone all around. Soft touch ,avoid you iPhone 4/4S from slip.