Protect your home from strays and rodents while allowing your pet free access with the Electromagnetic Pet Door. Pet door liner suits hollow and solid doors up to 2 ¼” thick. The pet door automatically unlocks and allows your cat or small dog to push through the flap when it senses the magnetic key on your pet’s collar. All other animals will encounter a locked flap. The kit comes with 2 magnetic collar keys; extra magnetic keys are available. Uses a9-volt battery (not included). The Electromagnetic Pet Door features a silent action transparent weatherproof flap. Three additional settings allow you to lock the pet door, allow your pet to enter but not exit or allow your pet to exit but not enter again. The door opens only for pets wearing magnetic keys on collar so you can keeps out strays. See our full list of pet doors!