Product review (5 stars): Excellent, installed quickly, keeps my house warm.
I am using this for the vent out of my microwave, installed very easily, I just screwed it right over the other vent after ripping out the flaps.  A can of almond spray paint and it blends right into my house.  I just wish it came with screws, I had to dig through my screw jar to find screws for it.