Product review (4 stars): Best one I found, but still not confident it'll hold up
It's a good unit that includes the parts I consider essential - the 6" collar, a damper and a screen.
The damper bends super easily, and the screen is barely held in place. I expect
to have to get on the roof to mess with this every so often.
It also has drain holes in the bottom for condensation. This makes sense, but it would be nice if the instructions addressed that for the installers. They didn't seem to think it needed shingles underneath (sigh).