Can these be used with external hard drives?
It can be done, but we don’t recommend it because of how sensitive hard drive transfers can be due to USB transfer speeds over long distances (6 feet or more). You will definitely experience slower read/write speeds over any of our USB extension cables.
Best practice would be to connect the external hard drive directly to a computer. If you need to run the drive over a long distance, consider a NAS server over Ethernet. Ethernet is a much better standard for data transfer over long distance than USB.