A snap-on accessory, printed in two parts. The base is modeled on the included spool holder, and holds well to the top of the Mk3S+ frame. The top is a bit more than half a torus, opened up.
I made it because looping the filament over the top of the spool holder, or over that steel plate, seemed to be inviting snags.

Modeled in Blender, and run through PrusaSlicer.

GCode has a pretty thick raft, and the final item needs a bit of whittling to remove support material.

CC0.