General purpose 40mm to 80 mm fan duct

NOTE: V3.1 of the duct was just uploaded to correct a mistake in the 40mm fan 'grid' orientation which made it impossible to print without supports. The screenshots still show this version (3.0) but the STL will display the correct design (the 40mm grid rotated 45 degrees).

This is a general purpose 40mm to 80mm fan adapter. This duct should enable you to usean 80mm fan in combinatie with anything that otherwise requires a 40mm fan, for example some extruder cooling fan duct.

Designed to n