Product review (5 stars): Don't you love how you are expected to review every item on ...
yup, it's a wall cap...it fits 3 and 4" ducting.  does what it says it does.  Don't you love how you are expected to review every item on amazon?  This is one of those items that gets a 5 star or a no star...basically it either arrives or it doesn't because there's not much else a wall cap is capable of doing.