3'' 4'' 5'' 6'' Inch White Plastic Duct Inline Hose Reducer Increaser. Connector to Vent Adapter 3 4 5 6 Inch // 80-150 mm

We ended up using this to attach a standard 3 inch flex vent hose to a portable air conditioner. It worked nicely.

Works as it should. Takes some encouragement to get the ducts to fit.

Does what the description says

This product still met my need. But upon receiving it the fatter end was warped. I could have 3D printed one myself but I did not have the time. Next time I will make time.