Hon&Guan Duct Damper 4 inch, Backdraft Damper One-Way Airflow Vent Damper Backflow Preventer for 4 Inch Duct Dryer Vent Hose

I am using this back flow preventer inline with a mechanical fan as the purge for my sauna. Works great, installed some fine mesh hardware cloth over the end to keep out crawlies and doesn’t seem to affect the operation. Closes nice and smooth without the normal tinny bang. Super easy to install in a 4” access hole with a dryer diverter tip, perfect fit so it is true to size as advertised.

Due to the construction of my home, i was unable to exhaust my portable ac unit through a window. I decided to run a vent through the attic access. Needed this to keep bugs from getting into the house. Works great.

I modified my exhaust vent and added this backdraft damper to reduce hot air and anything else from coming in when the unit is not running. It would have been better to install the damper in the far end of the duct (close to the window), but I would have needed to buy and modify a whole new window kit to make that work. Plus, my window does have a screen. The damper works well.install tip:Be sure to orient your damper so that the hinge is in the vertical position. This will ensure both flaps close properly with no air flow.

Good product

Cheap and Flimsy. I can tell straight out of the box that any amount of pressure or debris and the damper flaps will get stuck open or closed. Spring is super weak. I'm not even going to install it. Quit making garbage. I would rather pay a little more and it be usable.

The butterfly vent works as it should, but I almost immediately broke one of the retaining pins as I was fitting it into the shed wall. I glued a small nail in its place, so an easy fix, but I was disappointed with the build quality breaking under the moderate stress of fitting it into place.Otherwise it was fine. It fit the vent properly, without any modification or shims.

Works like it's supposed to.

Excellent quality.

extremely poor manufacturing quality. do not purchase. pin for backdraft damper flap was too short - didn't even stretch the length of the duct and customer service is terrible.