Product review (5 stars): Everyone should have one of these!
Every house with a dryer should have one of these.  Before I installed this vent seal the cold winter wind blew through our dryer chilling our house for years.  The traditional dryer vents with a flop dow door never closed tightly and they are a huge source of infiltrating cold air.  Installation was easy and made a gigantic difference. No cold air at all comes through he vent.