Getting the air to vent out of a soffit is not always a simple task. This hood or vent has everything needed to make a smooth passage out of the house - mounting flange, removable back-draft damper, and bird screen. And you can add the optional snap-in duct adapters for 4", 6", or 8" ducting.
(NOTE that this vent requires a wide soffit for mounting - at least 20". If your soffits are not that wide, the PRMX-SV401 may be more suitable.)
Some thought went into the design of this hood. Air doesn't like to make abrupt turns. This hood is effectively curved to allow the air to flow out smoothly. Using a "button-louver" for this task strangles the air. It's only slightly better than just leaving the duct open to the attic. If the air is not "thrown" out of the building with a decent amount of velocity it will be drawn right back in through the nearest opening like another soffit vent.
Thought went into the design of the water protection as well, and the damper itself is tighter and better fitting than most.
Beware of soffit depth 
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