Intended to extend usb 3 from back of desktop to side for connections. It will not work with devices that work when plugged in the same port without it. Both usb 3 hard drive devices have their own power adapter. I tried plugging in other usb devices such as a webcam, microphone, and a mouse. They all work. My guess is that the usb 3 hard drives do draw power from the port even though they have their own power adapter. Still, the devices worked on the same port without the hub. I was only trying one device at a time on the hub so it is not a total power draw that is the issue.