I've made this HeatSink Fan Duct to fit out a cheap "J-head Hotend Short distance" bought on EB with two 30mmx30mm fans. The first fan blows air into the heatsink and the second one extracts it. It is also usable with a single fan. The heatsink has an outer diameter of about 22mm, and a standard mount diameter of 16mm. I've been noticed that they are the same as the E3D V6 Lite6's dimensions. This fan duct has been designed with FreeCAD 0.17 and is parametric, so you can adjust some dimensions in the spreadsheet. As some parameters combinations are impossible, FreeCAD will either ignore your choice or just crash. Feel free to use and share this design. Good design is hard work, donations are welcome and feedback is greatly appreciated.