REQUIRED FOR: WALLS
This Tunnel Extension is required whenever the SureFlap Microchip Cat Door is to be installed into a Wall. The Cat Door already has a 70mm tunnel, and each extension is suitable for up to an additional 50mm in depth. For example, 1 Tunnel extension will accommodate a wall up to 120mm depth. 2 Tunnel extensions will accommodate a wall up to 170mm depth. 3 Tunnel extensions will accommodate a wall up to 220mm depth etc.