There are several designs on the net for holding filament to a spool but this is my solution and I have been using it for a few months. I thought others might appreciate it. I find it works perfectly for spools from ProtoParadigm.Just print it out. If you decide drill out the filament hole, be careful, If the hole is too big the filament just slips out.I uploaded the scad file for those who want to make their own. The parameters are: SPOOL_WIDTH = 74; SPOOL_RIM = 6; SPOOL_RIM_OVERHANG = 1.5; FILAMENT_DIAMETER =3.2;