This works perfect.
Nice Matting product between 2 Four Inch Female ducts.
The fans come with female vent connections, even though you need to attach a hose or stove pipe to conduct the air outside where it can't cause any harm.
Seems like the fan manufacturers have it all backwards.If you install one of these male to male pipe adapters then it's easy to connect that foil flex hose to these and then an outdoor vent.
I had to use a crimping tool to lengthen the crimped/fluted area to get one of these to fit into a Nutone fan output vent.
Didn't use it as it didn't fit, cost of return postage greater then the cost of the product so dumped it.
I was trying to couple a flexible dryer vent hose to the back of my machine, but since both the vent and the hose were 4" in diameter, I needed a coupler.
Ordered two of these, and they are complete garbage.
The ends appear as if they are easy to crimp (to make them small than 4" which is the whole point of a coupler) but they were impossible to adjust.