This is a filament guide which can be mounted near the extruder to reduce friction of the filament when entering the extruder to a minimum. It uses two 608er ball bearings and can be mounted with two M4 screws. Don't tighten them too hard (like I did as you can see). Printed and used for my Multec Multirap M420.I've printed this with 0,2 mm layer height, worked perfectly. When the bearing seats are too tight grind them down a bit.