4 Inch Draft Blocker Backdraft Damper Duct Draft Stopper One-Way Airflow Ducting Insert Backflow Preventer Inline Fan Vent Deflector

This damper worked perfectly to solved my problem. It is quiet and installation was simple

Just what i needed. Fit and worked great.

The flaps would rub against the bottom of the damper. I wrapped a paper clip around the bottom part of the rod to make a washer and cut off the excess. This raised the flaps high enough so they no longer rubbed. The damper must be installed with the flaps oriented vertically (like a door). When connecting the damper to the duct work, the crimped end off the existing duct will not fit into the damper so the crimp needs to be cut off and the damper will slide into the duct. When installing a sheet metal screw, there's no issue on the supply side but on the exhaust side the screw must be either at top dead center or bottom dead center so it will not interfere with the flaps opening. Once installed, the damper worked great and stopped the cold outside air from entering the stove exhaust.

Was hoping it would be sensitive enough to use on my air exchanger at low speed and it is. Exactly what I needed.

I had a high volume of backdraft coming out of my over the range microwave making the kitchen 12 degrees colder than the rest of the house when it gets cold. I played with the baffle that came with the microwave, which involves taking down the microwave each time, bouncing between allowing it to work but really not stopping any backdraft to it getting stuck preventing any stove venting getting through. If I had bought this 17 dollar (6in black) item before this last cold spell I would have saved hundreds of dollars on heating. Everything is quality with this. For such thin (lighter is better) sheet metal the vanes are perfectly flat and square making full contact with the generous gasket keeping all air out of the house. The lowest setting on the vent fully opens the vanes. Even the paint job, where only a 1/4" section can be seen when installed, looks high quality. Easy to install just pop off the vent cap outside, drop this in to the vent pipe (I then duct taped it because I didn't by a clamp) then tighten the vent cap back on to the other half of this.

I installed this inline for my over the range microwave oven. The damper that comes with the microwave oven wouldn’t work properly with a rectangular to round adapter. I tested this before final install and it worked fine. Just be sure you have the flow direction correct. I did find it difficult to get the aluminum vent pipe to mate with the damper. I finally got it then taped it real good.

If this vent is installed with the air flow going down, the springs will be challenged to close the vent due to the weight of the fins. Likewise if the orientation is horizontal with the hinge flap horizontal, the spring will struggle. The construction and fit is solid with a good seal when closed. Will do the job keeping in mind these conditions.

This gadget worked great! Solved the drafty issue.