Rack USB3 supports 3.5 "and 5.25".

Contrary to what the photo shows, this rack is delivered with an adapter 5.25 ''. The picture shows the rack without the adapter, so version 3.5 ".
It can therefore be mounted in the location of a floppy drive or a DVD player.

This rack is necessary to add two USB3 ports on the front of your turn. It requires a double USB3 socket, free on the motherboard. The connecting cable is long enough that the rack is installed in a large tower case. On my motherboard, the connector is at the bottom, I put the rack in 2nd position from the top, just under the DVD player.
Screws are supplied for installation and USB sockets have insertion forces quite correct. No need to force to introduce a plug.
The course USB3 devices are recognized immediately, the rack is actually a extender.
Note that the USB3 ports have 8 contacts instead of 4, that is why a USB2 extension does not operate a USB3 device to its maximum speed.