EASY INSTALLATION - With each Tunnel Extension adding 5 cm onto the Microchip Cat Flap, installation is Quick and Easy THICKER WALLS/DOORS – The Microchip Cat Flap Tunnel Extension provides a flush and precise fit for thicker Doors and Walls COMFORTABLE - Adding a Microchip Cat Flap Tunnel Extension creates a longer, more comfortable entry for your Cat NO TOOLS – Each Microchip Cat Flap Tunnel Extension can be conveniently glued into place for a secure fit. COMPATABILITY – The PetSafe Microchip Tunnel Extension is specifically designed for the PetSafe Microchip Cat Flap