Stray pets can often be a big problem, but this highly proven design provides a reliable solution. A cat wears a small magnet that doubles as an identification tag. A sensitive, fast-reacting circuit in the cat flap guarantees instant entry. Perfect for cats of all sizes. The easy to use four way locking system enables complete control over your cat's movements. Any cat can exit the door, but the cat must have the magnet on its collar to re-enter. This 7.75x9.75x4 inch package contains one electromagnetic cat flap and two super compact cat collar magnets. Requires one 9V battery (not included). Imported.