A holder for two filament spools, which mounts to 20mm extruded aluminum rails. Requires an M8 or 5/16th nut and bolt.

2-3 walls, 15-20% infill, no supports needed.

Spool Nut fits ½ inch nut.

V1 holds two 1-Kg spools without much wobble. V2 adds a stabilizer cover for the side rails. V3 adds slot clips to the side covers, in case of heavier or unbalanced spools. I suggest printing the Rail Test first to make sure this will fit with your printer tolerances.

-Created with Tinkercad.