This spool was heavily inspired by: http://www.thingiverse.com/thing:13395and was made to work with: http://www.thingiverse.com/thing:235925 / https://www.youmagine.com/designs/low-friction-um2-spoolholder Caps are a tight fit, and if you get "elephant's foot" on your "spoolMain" print, you'll be doing some clean up before you get the cap in there.Fits 1lb of loose filament pretty well, might make an adjustable one in the future.