This is intended for use with ABS. PLA users would want to add fans to cool the part, or find another fan duct system that does part + barrel cooling.The mounting faces would go onto the build platform. The intake duct might be optional, but it seems to eliminate intake wash vs. my previous fan duct designs.It should be buildable without any support material. The parts are designed for 0.5mm extrusion line widths.edit: this was a bit of a failed experiment. A barrel fan duct really isn't necessary for ABS single extrusion, and the exhaust turbulence caused a problem with the far end (Y+ end) of thin parts. So I haven't bothered updating it. I did repurpose the intake duct.I have gotten noticeable performance improvement when using this, with the special ducts to avoid exhaust turbulence from blowing onto the part being built:https://www.youmagine.com/designs/barrel-cooling-duct-for-mendelmax-2-jd-dually-belt-driven-extruder.