This is a single extruder version.I printed this on a Replicator v1 with MakerWare - 'Medium' setting (0.27mm layer height) with support, 100% infill, 3 shells. Support didn't work very well, but it fit into place after a bit of cleanup with an x-acto blade and works great. if printing again, I would try the high quality setting or decrease the layer height to 0.15mm.Available on Tinkercad: https://tinkercad.com/things/g5SIhhnUpxP?1) Prevents breakage of fan blades due to sticking objects into moving fan (aka fingers). 2) The Replicator extruder fan blows air onto parts as they're being printed, causing distortion, curling, etc. The fan shroud prevents air from being blown onto objects during printing.