Product review (5 stars): Great for DIY'er.
Perfect!  You can't find these locally in Home Depot or Lowes, and a local guy wanted $90 to intall one off of his truck.  I had to trim some flange plastic to get a perfect fit (issue with my old duct, not this product), and it's been performing well ever since.  Flaps open easily, as expected.  Nice item, great price.