20140508 UPDATE: New version 3 available in my list of items. Much improved design which prints faster and handles multiple spools much better. I usually bounce between several colors or materials when printing out stuff and the process of swapping out spools on my Rep2 and my Creator X is a PITA because some of the spools I get are those new, skinnier, but taller, spools that Makerware sells, or those spools that come from Flash Forge which have tiny-sized holes. They don't fit well on either unit. In short, whomever designed them or approved their use should be made to walk barefoot through a room full of Legos. Twice. I decided I'd create a new spool holder that connects to the Flash Forge Creator X case (and a later design to fit the Replicator 2) which holds not only multiple spools, but spools of several different sizes at the same time. To start, I needed vertical arms on which the crossbar holding the spools rests. For this, I went to Home Depot and purchased a 4 foot piece of .75"x.75" square aluminum tubing for about $15 http://www.homedepot.com/p/Everbilt-48-in-x-3-4-in-x-1-16-in-Aluminum-Square-Tube-40630/202183563 I also picked up a round bar of 3/8" Aluminum bar stock (it measures almost 10mm thick) for $5 to serve as a crossbar, which will hold the spools http://www.homedepot.com/p/Crown-Bolt-3-8-in-x-36-in-Aluminum-Round-Rod-49380/202183519?keyword=aluminum+round+bar+stock From there, I grabbed a hack saw and measured the square tubing and cut it into two, 18" pieces Then, I went into TinkerCad and created the "seats" (the parts that attach to the Creator X case and hold the vertical bars) Then, I created bar end caps, which plug into the ends of the square tubing, to hold the 10mm cross bar on which the spools rest. From here, I started thinking about how to mount different-sized spools while maintaining low resistance so the spool spins easily. I came upon the idea of using a 3D printed hub for each different sized spool which has an inner diameter of 30.05mm to keep rolling resistance low, I went to Amazon and bought 2 packs of (10mm I.D. x 30mm O.D. x 9mm W) bearings (5 pieces in each pack) for $12 (including overnight shipping!)\ Http://www.amazon.com/gp/product/B00JD4T4TC/ These bearings will be slipped onto the crossbar at equal intervals, then each will be glued into place with 1 drop of Krazy Glue (crazy, right?) From here, any combination of different sized spool hubs can be slipped onto the 30mm O.D. bearing casings, and the bearings allow the hub to spin freely, reducing strain on the feeder mechanism for the printer. Plus, it can hold 4 or 5 different spools (different-sized ones too) so I have easy loading/unloading when swapping spools, and somewhere handy to keep my open spools. Swapping out filament colors/types will be far easier. And, the new location directly above the extruder, means the filament has a more direct route into the extruder(s) so I don't have to use the tubes if I do not need them. Oh...it doesn't interfere with the 2 existing spool mount locations so now I can choose one of 6 different spools of filament to use and, it's removable if you need to move the printer around.purchase the parts linked to in the description print out the parts in the STL file assemble