Seal Backdraft Shutter 4 Inch Inline Extractor Fan Backdraft Shutter Quiet Rubber Flaps, Fits All DN 100mm Ducting/Made from Recycled Plastic in DE

It does what it is supposed to, rare these days. Others have said it was too small, so either there was a duff batch previously or their pipe wasn't 100mm, (4 inches). The silicone membrane also laid mainly flat, but it is possible to gently smooth it out from where it is gripped by the central bar as you can see, it lies perfectly flat, it is not intended for insulation, just to stop the draughts, and be light enough to open when the fan is on. Mine fitted snuggly in a100mm pipe,the rubber fin gasket compressing to seal. Due to the poor original fitting of the pipe, I then discovered air going around it between the wall and pipe, coming into the room thru the fan casing. It is therefore worth sealing inside and out if accessible, to ensure no gap between pipe and brickwork, before condemnation of the product! My wall faces north across a field,and the shutter has stopped the wind rotating the fan in reverse, thus preventing a cold draught in the bathroom. It has proven silent in operating thus far.

Works well, nicely made and a good press fit into some horizontal 100mm plastic duct coupling. Only criticism is the price (paid £17).

Would not recommend, the rubber seal is very thin and was sealing properly as it's very flimsy. Ended up throwing it straight in the bin

Really good product. Looking to purchase another 2 for other vents around the house. Finally, no more being woken up in the middle of the night by clacking plastic shutters!Whist I’d agree with other commenters here that if this product is placed inside 100mm / 4” ducting, then these shutters are a little small. However, if they’re used how I’m using them -pushing them inside the air vent grille (which sits inside the ducting), then they fit perfectly, making a very good tight seal. I’d suggest the instructions to “1-insert and 2-push further” doesn’t help with this as this can mean the shutter is now out the other side of the vent, and into the wider ducting. I’d also say that as long as the shutter is pushed towards the back of the air vent, the flaps can still open fully, unhindered by the grille. I’ve added some pictures which I hope illustrate the the use of this shutter inside an air vent grille.Brilliant product!

They attach perfectly to the end of the Addvent 100 series extractor fans. So just remove the fan from the ducting, attach the backdraft seal and gently insert everything back into the ducting. Currently working well.

Product looked good. Outside rubber seal good. Like others I think the central bar needs to have a more permanent fix. Even when I was fixing into pipe it kept coming off. Flaps were a bit too flimsy also when I was fitting the wind was making them flap open. From the wrong side. Awkward to fit because of its flimsy construction. Yet to see if it reduces the air ingress. Very pricy product misleading a little. Lots of more sturdy products on the market. Shame as idea was very good. They just need to sort the design out better.

I fetted this into my 110mm out let dryer vent on the outside off the wall i had to apply some electric tape around the rubber seal util it fitted snuggly in the pipe i very carefully apply some sealant around the edges a few hours later we noticed a difference the kitchen is warmer i have alreadt ordered another one for the inside kitchen wall i will give this a A++

So jury is out ATM as to whether this is doing the actual job it's supposed to. When it arrived I was disappointed with how flismy it seems - but it fits well and was easy to attach so now it's a wait and see if it lasts/does the job it needs to