Product review (4 stars): Protect your vents
This is practically the only product that I could find that fit my needs. I was looking for a cage to put over the vents on my house because birds have been getting in and building nests. They have large universal cages that stick out about 6 inches at Lowes, but I wanted something more low profile. I found these and they fit the bill. I just happened to need four, so the fact that they came bundled as four was convenient for me, though for the person that only needs one or two its a waste. They were as easy to install as any other vent cover and they seem to work both venting exhaust and keeping the birds out. I think they look much less conspicuous on my house than if I had the larger cages from Lowes.

Of note, the dryer vent I replaced was made by the same company, and the dryer exhaust is apparently potent enough to gradually degrade the color and structure of the plastic. After a few years I could imagine it might be brittle or discolored enough that it would warrant replacing. Thats the only reason I gave it 4 stars instead of 5.