Small M5 to M6 Adapter to be able to use a Festo QSM-M5-4 push-in fitting instead of the original Creality Extruder plug, which couldn´t hold a tube properly. I Used a raft to print this but it might work without. I have not tested it without.

The model is already threaded. Works perfekt for me on the "vanilla" Extruder. The tube didnt move a millimeter since i installed the Festo fitting. You can get the QSM-M5-4 i.g. on AliExpress, maybe local Hardware-Store or from work like me...