This door has been a godsend in my household of two indoor-outdoor dogs and two indoor housecats. Our animals had been used to coming and going into our backyard through a standard pet door. However, after we moved into town with traffic, we didn't want our two cats outdoors. This electronic door has worked really well allowing only our dogs with the "keys" on their collars to go out. The cats tried for days to get out through the doors, scratching, pawing, and ramming the door, but they finally gave up. They must have thought the dogs knew some magical code to Open Sesame.We did not have a door that would allow us to insert the doggy door so our contractor cut a hole through the exterior wall next to our French doors. We used the door plus the wall install kit. Everything fit perfectly. The "key," a bell-shaped plastic unit with a circular base that holds the battery and screws into place is a bit bulky for our small dogs. The metal loop that comes with the unit is too light and bendable. One of our dogs lost the key in the grass, and we had to order another one at a cost of almost $20. I like that we can set the door to automatic use with the keys, to always open, or to locked.So far, we are very pleased with this electronic doggy door.