This is a cover for the BondTech BMG ReverseBowden extruder.
This eliminates the need for the housing for the filament sensor (if you don't use a filament sensor).
Do not use this and the filament sensor housing together.
This is thread for an M6 PTFE Connector.
3D Solutech ABS
Also tested at 0.2mm and it functions just fine.
Printed out of ABS plastic but any should work just fine.