Product review (5 stars): Keeps the heat in and cold out
I had one of these on my dryer vent for over 20 years.  Thought I would get a new one as I got a new dryer.  If I don't have this, the clothes feel cold to the touch (I live up north) and not dry.  With this, cold stays out and heat stays where I want it.  I do put a knee high stocking over the inside vent area as there are particles the screen does not catch. Highly recommend.