For dogs 80 pounds and heavier. Don’t guess the size dog door you will need. The most important measurement is not your dog’s weight. Make sure the dog door opening width is at least 1” greater than the width of your dog measured across the shoulders. The height of your dog door opening needs to be at least 2" greater than the difference between the height of your dog measured from the floor to the top of the shoulders and the clearance of your dog measured from the floor to the bottom of the chest.