Prusa i3 MK3 Filament Holder arm

thingiverse

This is an arm that can be printed twice--once normally, and once mirrored--and attached to the top of the Prusa i3 MK3 (and maybe the MK2 series as well) allowing you to store up to three rolls of filament on top of your printer at once. All you need is a 12 inch steel pipe and end caps for it. The pipe runs through the first arm, then through the second arm, with the caps screwed onto the ends to keep everything in place. Make sure you print one normally and one mirrored, so you can put one on each side of the printer, then slide them outside as far as they will go. You may also need to rotate the model on the bed of your slicer to get the flat side down, and you'll definitely need to print with support. They are a bit loose, but that allows you to easily insert or remove the pipe.