Made for wall installations, each tunnel extender adds 50mm to the overall length of the 70 mm long cat flap tunnel. Multiple tunnel extenders can be stacked together to create a cat flap tunnel of varying length. This tunnel extender fits snugly onto the tunnel of the SureFlap Microchip Cat Flap and helps bridging walls of greater thickness. This Tunnel extension can be used to set the tunnel in the SureFlap Microchip Cat Flap or Dual Scan Microchip Cat flap for installation in a wall to extend. The Tunnel extension fits exactly on the tunnel in the cat flap. There can be multiple extensions can be attached to a tunnel of any length. The Tunnel SureFlap Microchip Cat Flaps and the Dual Scan Cat flap is 70 mm long and with each tunnel extension 50mm extended.