Required for glass installations, the Mounting Adaptor can be used with the SureFlap Microchip Pet Door and the Microchip Pet Door Connect. When mounting in glass, this accessory allows mounting in circular holes with a diameter of 294mm (min) to 320mm (max). The total diameter of the mounting adaptor is 380mm. The Pet Door Mounting Adaptor includes two parts, one for the exterior and one for the interior of your home. The Pet Door Mounting Adaptor is not required for wall installations, as our pet doors have internal screw holes to enable fixing to a wall.