Power Bank is an external mobile power for digital devices. You can take it everywhere and charge your phone whenever and wherever. It also named [external battery" [mobile power" [mobile power" [external power pack" [portable charger" etc. Power bank is a USB charger for phone, tablet, computer and others digital devices which can charge with USB cable and that require 5V voltage. Power bank is very portable for use. And it has two types, lithium ion power bank and polymer power bank. Lithium ion power bank made with 18650 lithium ion battery, and it normally can make 2600/5200/7800/10400mAh. It is little heavy. And polymer power bank made with polymer battery. It can make different capacity power bank. Especially high capacity like 5000mAh/6000mAh/7000mAh/8000mAh/10000mAh etc. It will be slim and light weight. Easy to bring and use. Any inquiries, welcome to contact Anita. Email: anita@maxcotech.com. Phone: 86-13977122746 Skype:anita.zhang9218