SureFlap 2" Tunnel Extension For Cat Flap and DualScan Doors

Tunnel extensions make installing a Sure Flap pet door in a wall easier by eliminating the need to build a wooden tunnel through the wall.

 

Just plug one tunnel onto the next until you have the depth of the wall covered, then trim the last one to fit. The manufacturer recommends using the adapter in addition to the tunnels for cat door wall installations.