I saw a few around and modeled one on richgain's version. It's two parts, the duct and the bracket. You might need a different bracket as this one is made for a Greg's extruder. But if gives 16mm or so of adjustability in height for different hot ends. NOTE: I have been told this will not work with Prusa V2, refer to the comments. Inside I have ducted about 30% of the air to the side the fan is on and the other 70% around the revolve to blow from the other directions. I based it on a 60mm fan because that's what I had on hand.You'll need to have your printer printing bridges well. I had to rig up two fans blowing from different directions to get it to print, but now I have it I can print bridges pretty nicely.The bracket replaced the x belt holders, so if you design your own you might want to include "teeth" to grip the belt as I have.You'll need a couple of 3mm bolts and nuts to assemble the duct to the bracket.P.S. If you have problems with the initial inner ring not staying connected to your heatbed try the version I have made for Dracus89. It has a .5mm fill on that first ring to hold it down. You will then need to cut it out once printed so the hotend can pass through it.