I have a MakerGear Prusa Mende, and they included a PTFE filament guide tube. Its fantastic at keeping the filament from catching on anything as it is routed to my extruder; however I wanted to clean it up and provide a permanent point so that my spindel feeds into the tube flawlessly.My guide tube is ~4mm in diameter, the guide holder front (the long column extension) has an inner diameter of 4.25mm. Print the part. Insert the filament tube into the long extrusion end. Use tape or glue to make a tight fit. Mount the holder to the frame with some extra washers and two nuts.