We have one in the sliding glass door in the dining room, it leads to the bar (which is not airconditioned year round) then there's one in the bar leading to the backyard. The backyard is surrounded by a 6 foot high privacy fence. All five of mine use it they range from 3lbs to 14.2 lbs. The door opening measures 5 in by 7 in. The only problem they have is getting by the guard dog
