Install your Electronic Pet Door in thicker walls with a Wall Extension Tunnel. The tunnel must be used with a Wall Conversion Kit (available separately). Each extension adds 2 3/4 inches to your tunnel. PetSafe® brand is here to help you and your pet live happy together™. Formerly known as the PetSafe® Electronic SmartDoor™ Large Wall Extension Tunnel.
Caution: Small children can pass through door. Read entire statement.