Product review (1 stars): Very noisy, two out of four flapper covers broke off within a year
Although these vents look nice, it turns out they have at least two VERY major design flaws.

1) On any "windy" days with gusts much above 10mph, these vents make an awful racket as though somebody is banging on the side of your house with a baseball. I never experienced anything like this with the previous vents on the house.

2) During this past summer, a thunderstorm rolled through with ~35mph gusts.  I went into the backyard the following morning to discover that the hinge on one of the vent covers had broken off and blown into my yard. I figured this was just a fluke and bought a replacement vent. Fast forward to this past weekend when a winter storm came through with similar wind speeds, and a SECOND vent broke and blew off. The plastic hinges on which the vent cover pivots is a definite weak spot with how easily the covers are rattled around in any amount of wind.

UPDATE: well, it's official. All FOUR vent covers have broken within three years of installation.

Nov 2017 UPDATE: TWO of the replacement have broken. That's a total of SIX failures