BMG clone extruder adapter

If you bought an inexpensive BMG clone (like this one: https://www.amazon.de/dp/B08PZ1RKJK), you may find that the "pneumatic" coupling for the PTFE tube is permanently attached to the aluminium piece in the extruder. In case the coupling fails (these tend to break from time to time), you cannot replace it. This is a drop-in replacement for this aluminium piece, allowing you to attach a standard PC4-M10 coupling. Since this piece is much longer, you will likely not be able to use it with direct extruders without adjustments, bowden configuration should work fine.
The length extension is due to the possibility to use a wrench.

The inner surface will guide the filament in order to fit into the PTFE tube.

Capricorn PTFE tubes should work, too (if they have an M10 thread).

I will upload some other options (PC4-M6 couplings, more snug fits etc.) and the source file in the next days.