We have a very large dog, two medium size ones and three cats. We hoped for an economical pet door that would permit the cats to go outside while keeping the warm air and dogs in. Once the Petsafe door was installed and the cats discovered it, the large dog stuck his head into the opening to find out where his feline friends were. That was the end of the door as a functioning unit and it doesn't seem to be repairable. The little locking mechanism and strip are not on the door anymore and cold air is blowing into the house.I'm sure that this would be an adequate product in a home with cats only, especially for an inside door. In our home, this was a waste of money and will continue to cost us heating dollars until we can replace it with something dog-proof.