PetSafe Microchip Cat Flap Key - electronic key for PetSafe Microchip Cat FlapPetSafe Microchip Cat Flap Key an electronic microchip key that allows your pet to use the PetSafe Cat Flap. This tag enables your cat to unlock the flap from the outside (outside the home). You can grant access to multiple pets at the same time or replace an incompatible, damaged, or lost key. It fits most cat collars. Dimensions: length: 4cm, diameter: approximately 3. 2cm.