1. Case with battery build-in polymer battery capacity is 2900mAh it can charge and discharge in cycle it means you have two batteries make sure that your phone power can work double time; When charging you need not to take out the "case with battery" just as your phone original way; 2. "Case with battery" follow the design which not only can power supply but also protects your phone it's ultra-thin and fashionable feature will make your life more convenience and fun; Usage information: Please read the instructions carefully; High quality PU leather case with card slot; With visual window for convenient use