The Sleek Aluminum 4,000 mAh Power Bank has a rechargeable lithium polymer Grade A battery (14.8Wh) with enough power to charge smartphones, MP3 players and tablets with a total output of 5V/2A. The dual output lets you charge two devices simultaneously. It also includes a battery check button to ensure that you know how much battery life is left. The reusable power bank charges via USB-A to Micro cable (included), which can recharge the battery backup or other devices with a micro-USB input, like Android™ smartphones from Samsung®, Motorola®, HTC®, Nokia® and others. Input: 5V/1000mA. Output 1:5V/2000mA; Output 2:5V/1000mA. Power banks are permitted in carry-on luggage only, and at the discretion of TSA agents. Please charge power bank before initial use.