iPower 4 inch Shutter Back Draft Blocker, One-Way Airflow Ducting Insert Backflow Preventer with 2 Inline Springs Loaded Folding Blades, 4" Backdraft Damper, for HVAC Extractor Fan Vent, Range Hoods

This backdraft is excellent, fits well into the 4" stove pipe system, and is functioning quietly. I would buy again.

I live in a humid area. So to prevent my bathrooms from getting humid, I simply went into the attic, cut the 4" flexible duct coming from the bathroom exhaust fan going to the soffit, and inserted one of these between the two cut ends of duct. (is a ONE way shutter so just be sure oriented in proper direction) Did this for four ducts. Worked perfectly.

added to a dryer vent hole to help keep the outside air and critters out. Valve flap only opens when the dryer blows out, otherwise it's sealed shut with a foam membrane. Dryer has no problem overcoming the spring tension when it comes on, the unit is galvanized but we'll see how long it lasts with hot moist air coming from the dryer. Easy to install to existing piping and used duct tape to create a nice tight seal.

It was a bit out of round and needed some adjustment, but afterwords it did fine. Blow in one side & it opens easily then it closes tight.

This duct is not 4" to fit inside snuggly into a 4" pipe. Like others have stated many other issues with this beside the size. Poor quality, poor design, poor manufacturing.

Mixed opinions on this. 4 inch flexible duct does fit around it but I have mixed success with compatibility with fitment with other rigid duct work. Couplers might be needed. In a pinch I made some cuts to squeeze this into another 4 inch rigid connection. My other feedback: the springs are too strong, I found a flap stuck, and the foam seals are too big reducing air flow (shown in picture where i cut smaller). Im using these to prevent back draft on an inline bathroom exhaust fan where volume matters. I found this damper reducing the air volume. (Shown in picture) In a time pinch, I rendered 1 of 2 springs disabled and cut the foam seal in half. Note, the little compression end piece holding a flap "rod" fell off. I had to work around this when it was lost. Overall, I had to stick with this product due to timeline but not crazy about it. Did I get it to work, yes. Am I confident it is problem free in time - no.

The draft stopper works. It has a rubber gasket it bumps against so is fairly air tight. It also keeps out rodents because it is a 1-way flap. This was one of the better prices I found

I purchased this because I recently noticed my dryer was getting moisture in it from outside (humidity). This seems to have resolved the issue and has kept the outside humidity from entering the dryer through the exhaust vent.

I bought this for over the range microwave vent. It works well

So far we’ve redone our entire home with this style of Backdraft protection we use the 6 inch for our kitchen ventilation and the 4 inch for our dryer and our bathrooms. Pretty cool design that it fits into an existing home Depot vent cover one thing that should be noted is that you need a fair bit of Airflow to happen in order to get the two little lever doors to open. So you’ll need a strong fan on the other end for installation. We used a little bit of cooking oil around the rubber gasket before inserting it into the aluminum tube. Be careful when you’re doing this. You don’t want to rip rubber gasket. Also, before you put the vent back into the wall, check to see if there’s any little spaces where air can still fit through on the sides and you could line it with just a touch of duct tape so that all the air passes through the two levers and not on the outside. Hope that makes sense.

Évacuation ventilation salle de bain. Empêche le froid l’hiver e les mouches domestiques d’entrer les autres saisons Très satisfait.

Product is 5.75” not 6”…. Even with crimping cannot get to fit properly

I used it to stop any back flow of air in to my exhaust duct on my grow tent. It has a thick foam seal when closed, which works well. The problem is the hinge for the shut off, has gapping which allow air through. But I figured out a fix.