Just another aid to guide the filament through the feeder. In combination to Roberts spool holder and extruder it works well.Print all parts, Guide and back bone screw together, put rollers together and slide on the shaft then screw on the end plate. I used Cura support structure for "filament Guide " part. I tapped the holes for the cap screws but you maybe able to get them started without one.If there are problems with the design please let me know. don't just give a bad star rating so adjustments can be made so everyone benefits.