These parts allow to add a PTFE filament guide (also known as reverse bowden) from the extruder to the printer's frame, and optionally to for example a filament storage solution. It makes for a better and smoother filament path.
After it turned out I only used my MMU2s as a remote (octoprint) filament selector (multi material turned out to be a real challenge, and I never have the need for multi colour), that has it's own set of quirks, I started to think about replacing it for a much simpler system.
My requirements were simple; have a fixed filament path, and have up to 5 filaments readily available. I also wanted to have easy access to all parts just in case something gets stuck (got tired of unscrewing these PTFE tube connectors)
After getting intrigued by https://www.prusaprinters.org/prints/52352-magnet-filament-coupler and it's simplicity, I asked for a .step file which allowed me to extend its usage to more than just a coupler. The design works just great and I only adapted the design to use magnets with a 5mm height as that was what I had available.
I then added a multi-magnet holder to mount on the frame (derived from the MMU2s frame mount), and a modified extruder cover to hold a magnet as well (derived from the MK3s+ part - the magnets do not interfere with the sensor or magnets inside the extruder body)
The f3d/step files are included and parameterised to adapt the design to your own needs or to hold different magnets. The f3d file for the original magnet cap can be downloaded following the link above.
The author remixed this model.