This is a reel for the nylon filament. Or, any kind of filament you want to use! I ordered some nylon filament and it did not come with a spool. So, I made my own. This spool will require you to use the filament holder from octave.com. It is a free download. You could find some octave filament holders on this site, too!
I believe, now though, they are shipping the nylon on spools! taulman3d.com I am using it on my Afinia 3D printer.