Do *NOT* Buy tethertools "boosted" cables, if you're buying a boosted cable, buy the Ebay ones. Why? They're produced in the same factory. I've taken both apart, they have the identical QC check stickers, same parts, same PCB... in fact the solder job on the £8 ebay cable was far superior to the £50 Tethertools one!
Interestingly the PCB passes the USB2 connections straight through, and only runs a signal amp on the USB3 lines, presumably because a straight 5m cable is within USB2 specs and a split mode hub amplifier was hard work.
http://www.ebay.co.uk/itm/5m-USB-3-...862782?hash=item3a7722a6be:g:ArMAAOSwyQtVr3Vn
I bought the tethertools one when I was having issues tethering and thought the cable was at fault, thinking foolishly "Ahh, must be my cheap Ebay cable."
Nope. Same damn factory.