This is a Insert for Bosch GCM 8 SJ. They are no longer deliverable, so we made our own.
It's a zero tolerance insert. You have to print it and cut slowly into it. A little bit of sandpaper gets rid of the fringes.
Made by Q-tec GmbH
https://q-tec-gmbh.de/
The author marked this model as their own original creation.