Yet another filament spool holder

I designed this for the Adapto printer. It mounts on a 20mm extrusion (horizontal only) but I also mounted it on my Makerfarm by using wood screws. The rods are 1/2" PEX which is stiff enough in short lengths. PEX is commonly available in hardware stores. This design provides easy spool replacement and flexibility to admit multiple spools. I have not tested the dual filament mode as yet. It may need a spacer to prevent the main extruder spool unwinding the other spool before it gets used.