Filament guides for these mounts: https://www.printables.com/cs/model/740680-mk4-mounts-for-universal-auto-rewind-spool-holder
You can insert a 6mm PTFE tube, but you lose the possibility of putting the filament sideways if it is already inserted into the hotend.
UPDATE: v2 - Hole for the filament has been moved lower to prevent unwanted deformation.
The author remixed this model.
Compared to the original, this model fits better on the frame, is a bit smaller and has a hole in the body for attaching unused filament.