This filament roller is composed of 2 parts. The top and the bottom. The top takes a standard 608ZZ bearing in the bottom that is used to roll the filament smoothly off. The idea is that you can have 2 rolls on this and switch between them as you need. I haven't tried using two rolls at once on this and could imagine there would be problems related to speed or when one printer finishes before the other. I printed the top supported in Simplify3d but I think bridging would suffice as well. Happy printing! Please post if you print! Released through my company Northern Layers: http://northernlayers.com