Product review (3 stars): At $18, it's twice the price it should be.
This vent cover is very nicely designed in theory, but.  The plastic is very thin and frail to the touch and eyes. I suspect that while doing yard work, simply bumping into it will snap off the covers.  The hinges are weak and the covers are VERY flexible and thin.  Maybe they are built that way to operate with even the weak of exhaust fans.  The mounting plate easily warps when screwing it into the wall, so I suggest using fender washers to reduce that problem.  It looks and feels no better than the vent at the local hardware store that only cost around $7.  Maybe the UV resistant materials added to its construction will help it outlast the $7 local version in terms of deterioration and losing shape, but only time will tell.

Having whined about all of that, I really like the double flap to keep out critters and wind, WITHOUT the classic screen which needs cleaning every week or more.  Should have been built sturdier for the price though...