(1)DO not used for charging,it is used for offering more usb ports to transfer file.
(2) The power supply can solve the problem of insufficient power supply, if you need work with a hard disk , then you should choose the with power supply , and please note ,please don't use more than 2 hard disk at the same time
(3) The power supply can improve the usb transmission speed

1. 100% brand new and high quality
2.Hot plug & play USB device

3. Fully compatible with USB specification version 3.0

4.With blue LED for power

5. ON/OFF switches activate or deactivate individual ports

6.Designed with 7-port,this compact USB3.0 high-speed hub is small enough for travel,and cable enough to meet your connectivity needs

7.Thespecification of the power supply is , 5V 2A.

Features:

7-port USB 3.0 hub, ultra-high speed transmission, generous design, reasonable interface layout, no interference
Features Each USB port LED is designed to control each USB device
Support overload voltage and instantaneous current protection, effectively protect the connected equipment and HUB itself
Conforms to USB 3.0 specification, supports high-speed 5Gbps bandwidth transmission, and backward compatible with USB2.0 / USB1.1
Free driver support for Windows XP / Vista / 7/8 and MAC with USB support