Product review (5 stars): Perfect fit
For the past few years I have had a pair of silly Swallows make a nest in my dryer vent.  I am always able to remove it before they lay their eggs bit I hate destroying all their hard work. I used this vent to replace the dryer flaps that the birds would crawl through on the outside of my home.  It is a perfect fit and I haven't had a problem with birds since installing it.  Bonus,  the cost was much cheaper here than in stores.