calimaero® 4 Inch Backdraft Exhaust Damper Seal One Size Fits All Duct Backdraft Damper Gravity Powered Made in Germany HVAC Damper Dryer Vent Valve Keep Cold Air Out

I needed this at the end of a 20 foot run of flexible duct. It fit perfectly in the 4 inch plastic flange I installed in the wall. I agree with other reviews that the plastic bar holding the rubber flap in place is pretty flimsy. I used some Loctite Fun-Tak Mounting Tabs to secure it. The manufacturer should have used a stainless steel spring instead of the plastic bar. The damper works great for me. 105 CFM bathroom fan pushes the rubber flaps open easily and absolutely no backdraft when the fan is off. I will buy this again.

I was a little skeptical of the mechanism but was lured by the thin dimensions. The product I received is basically junk. It is not as pictured. The flapper is not black plastic or rubber, but rather this light brown, very thin, very flimsy rubber. It doesn't have enough stiffness to even overcome gravity if the flapper is facing downward, and when facing upward the flap doesn't sit flat (I tried adjusting it a bit, as it's just friction-fit in place, but it is just too thin and cannot be made to sit flat). I don't consider this the same product pictured, and this substitute does not even function.

I was looking for a back flow preventer with minimal pressure drop that would seal tightly. I live in a condo with an ducted exhaust that sometimes has reversals that can bring smoke or odors into out unit. Out of the box the flapper was puckered but I was able to cut small notches to allow it to lay flat. life is compromise an I could not mount vertical because the weight of the flapper made it open and I was afraid it would not close for minor reversals. I was able to install it horizontal which appears to work pretty good.

I needed a one-way valve for the air vent on a project of mine and this fit the bill. It fits nicely into a 4” duct pipe and obstructs backwards flow nicely. This works perfectly.

Like others have said, the flap is so flimsy that it never really fully shuts. I like the idea of how this works and the size fits my needs perfectly, but I think the flap material needs a revisit

This damper broke when I used my bathroom fan, I had to replace it instantly.

Excellent product If you can’t fit a typical damper in old construction, flexible duct work (or dont have full access). This was exactly what I needed! It’s only 1/2 thick so you can wedge it right into the exposed duct without having to tear everything out.

I like the product. Only 1/2 " thick, makes tight spaces easy to have a hood backflow valve fit. I think the rubber valve closing won't gunk up like traditional valves.

We have a half bath in our house(built 2017) that was always cold. I've checked the insulation, wi dows seals, and even upgraded the heat run fron a 4" to a 5". Nothing seamed to improve the temperature in the room. I i stalled this damper i. The ventilation fan and within minutes the room was as warm as the rest of the house. Its currently -30°c here and the room is warm. 10/10 will install in every bathroom from now on.

Ce n'est pas des volets qui s'ouvre ou se ferme. C'est une simple membrane,qui se lève et se rabaisse.

Per la sua funzione ed in base al mio utilizzo direi che è ottimo

In contrast to other reviewers, mine seemed to fit just fine into a 100mm galvanized spiral duct. The flap is made of a very flexible type rubber, meaning it opens with very low fan pressure. The housing is made of ABS plastics. The flap does has a tendency to crease if not fitted properly inside its retaining bracket, so do take notice and flatten it out before installing. All considered i'm satisfied with its functionality. The price could have been a tad lower though. Also a 125mm model would be nice to have.

La valve anti retour n'est pas fixée sur le support mais à part ça, parfait