Vent Systems 4'' Inch Backdraft Damper - Backflow Shutter - Heavy-Duty Inline Springs Loaded - One-Way Airflow Ducting Insert - Inline Fan Vent Deflector

Product was used in an outside system ran from one home to a camper and it works exactly the way I thought it would sorry I don't have pictures if I'd a known I would have took pictures during the install

I had to work around the spindle a little. I used ring clam to tighten the female.

The good thing about this product is that it is made of metal and is likely to be very durable. However, it misses the mark on two key areas of functionality:1) The backdraft damper needs a lot of airflow force to open it. I turned the fan to max (around 100cfm) and it would not budge. Apparently, the springs are too tight.2) This unit is not flared out or in, so it can't be either inserted or fitted over existing duct. Instead, one would have to tape it on. It is the same dimensions on both ends, so you can't move it to another end elsewhere to get a different result. I tried to flare the existing metal duct to squeeze the duct inside this unit, but the metal was too rigid to fit in. I tried flaring the duct outward to fit over the unit but was also unsuccessful that way. The metal of both the duct and of this damper are too rigid to make that work. So taping is the only way to do it without cutting and possibly damaging either connection point.

Does just what it's made for. Thanks

This is clearly not the same item as the one in the ad. The one in the ad had two springs, which was the reason for me ordering it in the first place.However, I like this one... Unlike others I have ordered with single springs, in this case the single spring is strong enough to keep the leaves closed and should prevent rattling with slight winds but should function properly. I intend to order more; right now!