Product review (4 stars): Solid
It's a solid construction. Functions properly. Damper works well. And it looks very neat, once installed. The vent is a square shape, so it's easy to make a cutout on the shingles. Only negative is that the bottom 6" connecting collar is WAYYYY too short. I STRONGLY recommend pulling your ducting THROUGH the hole on the roof, connecting it to this vent, THEN installing the vent. Because if you try to install your ducting to the vent, after you've done your install, there will be no way for you to attach it, as the duct collar at the bottom of the vent does not stick far enough through the roof to connect to. You'll see what I mean when you buy this. I did it the hard way and just barely caught some zip ties on it. That is not the way to go about doing it.

Also, I'd recommend cutting the hole slightly larger than a 6" diameter. Maybe something like 6.1-6.2"