This adapter lets you connect a 4 inch air duct with mass produced 5.9 inch window vents. This has flanges for locking into the window vent like the normal window vent cover and even has space for the vent bird guard/bug screen to be placed inside. You will need to sand off a few millimeter deep lengths of edges on opposite edges of the window vent plate hole in order to fit the flanges through for turning and locking in (black sharpie marks on the vent in the photo show the approximate circumference of the vent plate hole to widen on opposite sides).
It locks into a 5.9 inch diameter A/C window vent plate and fits a 4 inch female air duct on the other end.
I use this with https://thangs.com/mythangs/file/195526 to exhaust air from my printer cabinet.
It can be combined with a 4inch ball valve blast gate model originally by mattcoon on Thingiverse https://www.thingiverse.com/thing:5200188. Those files are uploaded as additional files here for reference.
Commercial modification or resale of this design is prohibited without prior approval from Anson Liu (support@ansonliu.com)