A filament guide with a roller for even smoother filament feed than fixed ring. Designed for the Ender 3, easily plugs in to the back of the aluminum profile. T-shaped arm is both lightweight and strong with little material used. Length optimized for good operation with both low and high prints. Also allows you to put the spool holder more to the center.
Prints in 3 parts, extremely easy to assemble. A slit allows for installation without need to pull filament from extruder. Slight protrusions near where the axis is placed ensure small clearance of the roller from the base and smooth rolling; slightly sanding roller edges is still useful, but not required.
For those with trouble slicing the base model (it has some defects but works fine in Cura) or if you want to print it without supports for the teeth, alessi71 remixed the main part here: https://www.thingiverse.com/thing:3218716
I included it here with his permission for convenience and also rotated to optimal print orientation, use the file Base-FilamentGuide_Roller_V2_Rotated.stl
I you're using the Z knob, I made a remix that is longer and compatible with the guide: https://www.thingiverse.com/thing:3387796
Works best together with another of my guides, this one for extruder: https://www.thingiverse.com/thing:3122485
Print the base upside down, the axis and roller standing. The axis requires brim, other pieces not necessarily.