The cool new Automatic Locking Pet Sensing Door automatically locks and unlocks it's flap only when it detects a coded smart key attached to your dog or cat's collar. This high-tech pet door supports one to five smart keys and gives your pets unlimited passage in and out of the home, while preventing any of their friends from getting back in. The sensor's range can be adjusted from 6 inches to 6 feet and the door automatically locks approximately 15 seconds after it is out of range. This secure, sealed, weatherproof ABS frame with rigid polycarbonate flap installs in standard doors from 1 1/2" to 2" thick. Great solution for many pet owners, but hopefully your dog or cat actually returns.