If you need to couple a 30mm fan to a 22.3mm cylinder then look no further! The beautiful new E3D v6 fan ducts are injection moulded out of translucent blue polycarbonate. They are much harder wearing than printed parts and because they are manufactured to tighter tolerances they are significantly less prone to vibration.
These ducts are not compatible with v5 HotEnds.
This duct is available for download as an STL on Thingiverse. Thing:340312.