I had issues with the stock Ubis hot end from Printrbot so I ordered two E3D extruders and now I'm in the process of printing parts to fit a dual bowden carriage to a Printrbot Plus v2. This is the model I made for dual fin and nozzle fan ducts. They are designed to fit 40mm cpu fans. Since I didn't have the fans before I printed these, they came out a little warped but I still managed to twist them into a functional position. It uses M3 screws for the fans and one #6-32 to mount the ducts together. The design is solid though. It can rotate 360 around the hotend while keeping the nozzle tip in the center of the duct exit and clears surrounding mechanisms with 2mm clearance from the print. Next...Bowden extruder motor, dual bowden extruder carriage Also one of the solidworks parts has a rebuild error in it that I couldn't fix, it has no effect on the final product though.