This fan duct allows for using a 40mm axial fans, which are easier to find.If you're using a 40mm fan to improve cooling, be sure to use computer thermal paste on the upper end of the heat break. That will probably help at least as much as this fan duct does, even better combined with this duct. The fan duct clips onto the barrel without any extra hardware. For me, it seems to stay put and doesn't rattle much.The intake is optional, but I find this eliminates fan wash on the intake side. I haven't done any tests to see if this improves air flow, but I've found fan wash to interfere with part builds using ABS. I've made 10mm deep intake ducts before (also on YouMagine) but this is 8mm to improve clearance. It seems to work just as well. I'm including solid model files for easier modification by others.