I wanted to connect a drybox to my MK3S+ and not modify the extruder to accept a bowdentube.
This adaptor should be a snug fit for the rods of the spool-holder, a bowden-tube fitting with M6 thread gets screwed into the back and filament then runs along the sloped surface to the extruder.
The support clips onto the top rail and prevents the actual guide from rotating if it slips on the rod.
The author hasn't provided the model origin yet.