These mounting adaptors from Sure Petcare allow installation of the SureFlap Microchip Cat Flap, the DualScan Microchip Cat Flap or the Sureflap Microchip Pet Door in a window or wall, allowing the pet doors to be mounted in circular holes. Detailed installation instructions can be found in the user manuals for each product. The Cat Flap mounting adaptor at a glance: Adaptor to allow you to build Sureflap Cat Flaps into walls and windows For use with the Sureflap Microchip Cat Flap or the DualScan Microchip cat flap Dimensions: 30 x 30 x 3.5 cm Fits holes of 21 - 26 cm diameter 2 parts The Pet Door mounting adaptor at a glance: Adaptor to allow you to build Sureflap Microchip Pet Door into walls and windows Suitable for covering holes 29.4 cm – 32 cm 2 parts Diameter: 38 cm Optional tunnel extensions are also available to purchase separately: add extra tunnel length to wall installation. Please note: Cat flap must be purchased separately