Required for glass and wall installations, this product can be used with the SureFlap Microchip Cat Door or the DualScan Microchip Cat Door. When mounting in glass, this accessory allows mounting in circular holes with a diameter of 212mm (min) to 260mm (max). The total diameter of the mounting adaptor is 285mm. Using the mounting adaptor for wall installations enables you to install the cat door more easily because you can use it to fix the cat door to the wall without the need for messy adhesives. The Cat Flap Mounting Adaptor includes two parts, one for the exterior and one for the interior of your home.