Could be better 1

Sturdy and easy-to-install products. The mounting material and the fixing screws for the extension rails come to me subjectively but not very high before, so a star deduction.
The locking screws are tightened with a hex, which, however, at relatively little effort "auslutscht" the hexagon.

For the attachment itself, I have dispensed with the accompanying screws and dowels and taken my own 10. The original dowels and screws have to be 11er (but did not have correspondingly large drill to hand and I can dispense with the maximum load of 30 Kg handed me the little ones).