Well, actually, cardboard. We made one today from this link: http://www.thingiverse.com/thing:1550 Since I already had a crate, this was a good project! We have a plotter for drafting, so we had to get that working first, and then we printed the STL file using inkscape in real-size... a razorblade and a blister later, we had a spool that looks pretty good, and functions pretty good. I just need to find a dowel from somewhere, and we'll be in business.