The Sleek Aluminum 4000 mAh Power Bank has a rechargeable lithium polymer Grade A battery for charging smartphones, tablets and mobile devices with a total output of 5V/2A. The power bank's dual outputs allow you to charge two devices simultaneously. It also includes a battery check button that displays the remaining battery life. The reusable power bank charges via an included USB-A-to-Micro cable, which can recharge the battery backup or be used to charge devices with a micro-USB input. Power banks are permitted in carry-on luggage only, and at the discretion of TSA agents. Please charge power bank before initial use.