ThinkPad Stack is a versatile innovation that connects four popular accessories into one. A Power bank, a wireless Router, an external Hard Drive and a Bluetooth speaker, all designed into stack form factor which helps you make the most efficient use of space. Its modular design gives you the flexibility of bring only the ones you need. Multiple combinations of Options make it more than what you see!ThinkPad Stack 10000mAh Power Bank is the central part of the Stack family. 10,000mAh high-capacity enables a hassle free mobile experience wherever you go. A unique pogo design makes it feasible to power up other stack components at once.Dual USB charging ability provides high efficient fast charging to two USB devices at onceCharge up to 4 other stacks with stack them together easily and simply