For wall installations, tunnel extenders can be stacked together to create a longer approach tunnel to the SureFlap Microchip Pet Door or the Microchip Pet Door Connect when it is installed in a wall. The Pet Door Tunnel Extender fits snugly onto the 70mm long tunnel of our pet door. Each tunnel extender adds 50mm to the overall length of the tunnel.
PLEASE LOOK AT THE SECOND PICTURE, IT'S VERY HELPFUL.