SummaryI really like the original MakerBot Filament Spool holder, and most of the new spool holders for the kossel can't be printed on a 4" square platform. I modified the Makerbot Filament Spool holder to be compatible with open beam.InstructionsI used 3 shells and 30% infill, but I am sure someone else can get better results. Mine didn't turn out great. I have a lot of ears on the part to prevent curling, because this part is pretty much the worst case scenario for causing curl. The gap in the part is a tapered slot, which causes it to become clamped to the open beam when the fasteners are tightened. You will need M3 nuts and M3x 8mm fasteners.