Staywell Infra-Red Collar Key allows your cat entry through the Staywell Infra-Red 4 way locking cat flap (500 series). If you have more than one cat, you will need to purchase additional collar keys. If you use the same coloured collar keys as you originally purchased, no further programming will be required. However, if you prefer to use different coloured collar keys (Green, Yellow, Blue, or Pink) you will need to program each collar key to the cat flap