My enclosure has a built in fan over an opening. I wanted to be able to control where it vents out to (a nearby window), so I purchased 4in ducting on Amazon. This is designed to fit in my side-to-side window and be held in place with the sliding window.

The box is 44.5mm x 170mm x 150mm. The flange part is 100mm in diameter and 25mm tall, which should give enough space for 4in ducting to be placed over it and secured.

It also has four 35mm x 35mm x 0.8mm slots for some metal squares so a magnetic sheet can be secured on top as a cover while printing.

See my other model for what the other side of the duct is attached to.