Fits every spool with plastic ends that I've used since I got my first 3D printer in 2010.

Parts are properly aligned for printing in the correct orientation. PLA at 0.2mm layer height with 20% infill worked well for me. A raft keeps the surface finish consistent. Tracks require a small amount of easily removable support. 

The pin (x4), if you print it separate and scale it up a percentage point or two, will have an interference fit and push into place for a permanent connection with the arms. If you don't want to scale and print four pins until they work, print as-is and add a tiny amount of cyanoacrylate glue to the hole (at the ends of the x-arms) that the pin goes into but not on the shaft of the pin. 

The nut (x4) should be snug, if too tight, scale it up in the x/y directions by a percentage or two to get a looser fit.