Product review (5 stars): Seems to be a good way to attach the ductwork to the vent cap
Just installed this for a dedicated vent for a broan range hood (previous hood did not have an exterior venting option). I found a sheet metal square with an 8" circle in the center in the stovepipe section of the hardware store and used one of those 8" round duct starters with tabs you bend over and screwed that to the attic side of the vent cap with sheet metal screws. Seems to be a good way to attach the ductwork to the vent cap.