SureFlap Cat Flap Tunnel Extenders can be used to create a longer approach tunnel to the SureFlap Microchip Cat Flap or the DualScan Microchip Cat Flap when it is installed in a wall.The Cat Flap Tunnel Extender fits snugly onto the tunnel of our microchip cat flaps and multiple extenders can be stacked together to form a tunnel of any length. The tunnel of our microchip cat flaps are 70mm long and each tunnel extender adds 50mm to the length of the cat flap\'s tunnel.Please note: this product is not suitable for the SureFlap Pet Door and is only compatible with the SureFlap Cat Flap