The Staywell Manual Tunnel Extension is suitable for doors fitted with the Staywell Manual 4 Way Locking Deluxe Cat Flap (white woodgrain or grey) the Staywell Magnetic 4 Way Locking Deluxe Cat Flap (white or woodgrain) or the Staywell Infra-red 4 Way Locking Deluxe Cat Flap (white) that have a larger depth than usual. This means that an additional depth of tunnel is needed to allow the flap to be used. The tunnel thickness is 2