Rectangular fan to round output connector

Simple adapter to connect a fan with a rectangular output to a tube.
In my case used to connect the blower to my oil stove.
https://www.youtube.com/watch?v=9ED8GYfPu9o

Initialy made out of wood (as can be seen on the youtube video) but now replaced by a 3d printed part. The fit is much better and there is no more air leakage.
The diameter of the output tube and the size of the fan can be modified to fit your own project.
The fan I used came out of an old Cisco switch. 29xx or 35xx serie