A spool holder made for aesthetics. Instead of mounting the spools over the ordbot (in my opinion was not very attractive) it is mounted on the back of the handle plate next to your controller board. you must have either a weight or your powersupply mounted on the front y axis in order to keep everything balanced If your wondering about my feed guide, it is just a mashup of http://www.thingiverse.com/thing:109215 and http://www.thingiverse.com/thing:27574 (Had one leftover already from a printrbotplus build) I modeled a cylinder that fits inside the guide and screws into the makerslide endcap. This allows the guide to rotate freely as it feeds to the extruder. I printed at .4layers .2infill honeycomb and supports you will need 4 screws to mount this, screw in the top 2 holes first then do the bottom screws. I used some random 6-32's i had laying around.