For ease of access to the filament while loaded in the PTFE tubes I really liked the 'Prusa MMU2 PTFE Holder M10 Passthrough Adapter' (https://www.thingiverse.com/thing:3233579), but in my own setup I just cannot reach the back of the MMU2S unti very easily. So I decided to move the acces point for the filament further down away from the unit and use some PC4-M6 tube fittings.
The original coupler works great already, but I needed it to be somewhat bigger, and made some windows in it so I can actually see the filament inside.Since this coupler sits at a point where the filament did already pass when loaded, it is not neccessary to insert a piece of PTFE tube into the coupler itself.
The window do also allow to put an occasional drop of oil on the filament.
I don't know why the preview obviously shows a render error. The thingiview - View does not implicate that there is a problem with the model, and slicing with slic3r PE didnt reveal any problems either. Please let me know if you encounter problems slicing this with a different slicer.
Das Filament PLA
tom's infinity blue