We have thick stone walls, so had a new pane made for our window, installing a stainless steel gravity vent on the outside. This was initially paired with the 3D printed part using built in fittings to take a standard flexible 6 inch conduit. However, this meant that we could never close our blinds fully.
Which brought me to the latest implementation using a magnetic mount so we can seal the vent when the air conditioner is not in use, and just offer up the hose to the fitting when we need it.
The magnetic version uses a spare 6 inch flexible to solid adaptor that I had handy (I'm a bit of a hoarder), but you could easily kitbash something using the original part that I am also including in this collection.
(Adhesive is still curing in the photos, but will be trimmed back to tidy up the installation once fully cured)
Sized for 6 x 3mm magnets.