I made various tests with USB 3.0 hardware using CrystalDiskMark 3 (Benchmark software) and flow rates with and without extension are almost the same. There is therefore no significant loss with the extension cord.
The extension seems sturdy well made: the cable gives the impression of strength and is pleasant to use (as far as being a little computer cable).
In addition, the extension completely fits my needs: I bought a USB Hub HooToo® (Version 7 USB 3.0 ports + external power supply). However the USB cable provided did not allow me to put the Hub on my desk.
Since this problem is solved.
I would highly recommend this if your extension cart allows you to put an article "Shopping Plus".