Let all of your cats use your magnetic cat flap or replace your cat's current magnetic collar key. This PetSafe® Staywell® Magnetic Collar Key is compatible with Staywell® Magnetic Cat Flaps (400 and 900 Series). The collar has an elastic strap designed just for cats, but you can take off the key and use it with any cat collar. Your pet deserves the best. Trust PetSafe® to help keep your pet healthy, safe and happy.