Product review (2 stars): Cheaply made with NO SEAL!
Not wow-ing me.  The product is flimsy, with gaps between the plastic halves.

Worse, there is NO SEAL around the flapper on any side.  In summer you will still get some dryer air inside, and in any season you will get outside air and bugs in through the valve.

Still trying to decide if I even want to install this or send it back.