This is a collar to fit every standard 68mm diameter hole that is commonly used in the EU for installing sockets and light switches etc.
If you need to feed a cable into such a hole e.g. speaker cable, HDMI, ETH to some other HiFi equipment you can use this collar to give the hole a nice clean and protected edge.
Der Autor hat dieses Modell als seine eigene Kreation gekennzeichnet.