Pretty good, use with a screened window if you live where there are lots of insects.
I love the idea of this product and the filter part worked well.  I would have liked more air flow through it, but understand that to keep the pollen out, it doesn't allow max air flow.  The downside for me, has more to do with where I live...I live in cattle country and in the late summer/fall we have lots of flies.  Unfortunately, the flies were able to get into the house and also into some crevices on the filter so when I took it out for the season, we had a few days of Amityville Horror amounts of flies.  My poor hubby was killing 50 to 100 flies about every 1/2 hour and that went on for a couple of days.  So I guess what I would say is if you have flies don't use this in a window that does not have a screen.  Other than that I was happy with the product and yes, I do think it reduced the pollen allergens in the house as we were not sneezing as much as past years.
Rating: 3 stars