**UPDATE 4/28/16:
I have designed a filament guide that can be used in conjunction with this spool holder to help prevent the spool from being pulled off if the filament binds. The filament guide can be found here: http://www.thingiverse.com/thing:1526925.

**UPDATE 4/24/16:
WARNING: The filament may have a tendency to bind on your spool, and the extruder could pull the spool off of this spool holder. I ran a long unattended print last night, and somewhere around the 2 hour mark, it appears that the filament on the spool got bound up a bit, and the spool was pulled off of the holder. I will be designing a fix for this in the near future, but in the meantime, just be aware of this issue. (credit to jdalemarrowstone for pointing out this issue).

UPDATE 4/13/16:
I uploaded the files for the modified version that uses 608 skateboard bearings. Just choose the appropriate files for the bearings you want to use. However, i should note that I have not tried printing the 608 modified version myself. If you do, please leave a comment as to whether the bearing posts are the right diameter for a snug press fit. Thanks!!

This spool holder is designed to mount to the top of the Printrbot Play using the same screws as the spool holder that comes with the printer. It will adjust for spool widths between 2.25" up to 4.25". It uses ball bearings with dimensions: 0.625" OD, 0.25" ID, 0.196" Wide. These ARE NOT 608 SKATEBOARD BEARINGS. They were just what I had lying around from a past project. You can just search for 1/4" x 5/8"x .196" Bearings on ebay or amazon and take your pick. If there is significant interest in making these with 608 bearings, I would be willing to alter the files for that. I also am including the FreeCAD file if you want to do it yourself :)

The stock spool holder on the Play... was insufficient for me. For one, it doesn't really let the spool spin freely. And the other issue I had was that I bought a spool of filament that was just a hair too wide to even fit on the stock spool holder.