Product review (5 stars): Great roof vent
This really worked well for my kitchen exhaust fan, I removed the existing roof "mushroom" that was the previously venting some of the air- the rest stayed in the attic- not a good thing.  I used  a piece of sheet metal between the roof and this cap and cut in a 6" starting collar take off which allowed a tight connection of the straight duct to the cap.  The end result was all that exhaust air getting out to the roof- just what I needed.