A 200mm filament spool very similar to the plastic ones used by suppliers like protoparadigm. The thickness is reduced to the hub thickness (one side of the plastic spools is inset) so it should be compatible with any spool holder if cut with the 52mm inner hole. I intend to use them to spool up my few remaining loose 1kg batches of filament.
The design is for 3.2mm (1/8") MDF.
Choose one of the inner holes: Either the 52mm hole for plastic spool compatibility, or the 8mm hole if you just want to put it on a smooth rod. Of course you can draw your own central hub to any size.
Cut two copies. The design is optimized to fit in a square of material. Take all of the spokes from both cuts and dry fit. Then glue (only 2 or 3 spokes really need to be glued, the rest aren't going anywhere). Two of the spokes have holes for securing the start of the filament.