What accessories do I require for installation?
You likely don't require any mounting accessories:
- If you don't currently have a cat flap or an existing cut out; or, if you're upgrading from another device with cutouts less than 200 mm width and 200 mm height;
- and your door is less than 55 mm thick (typically the case in the UK and most of Europe).
Exception: In the rare case that your door has a metal lining (<1% of installations), this may attenuate the microchip read range (Note: this is the case with any microchip cat flap). In such situations, expanding the hole may improve the microchip read range - which may then in turn require a Standard Round Mounting Adaptor to cover the enlarged hole.
If your door is more than 55 mm thick (more prevalent in Scandinavia), you may require:
- A tunnel extender;
- If your door is between than 60 and 90mm thick you may require 100 mm screws.
If your cutout is slightly larger than 205 mm width or 205 mm height (or 205 to 270 mm diameter hole), you may require the following to cover the slight gap:
If your cutout is quite large (i.e. not covered by a 280mm outer diameter Standard Round Mounting Adaptor), you may require a:
- Large Mounting Adaptor. These are available in three variants depending on available space and geometry of your existing cutout (Large Round, Large Square, Large Squircle). These adaptors cover up to 315mm.
For installations in glass (212 - 270 mm diameter) you will likely need:
If the diameter of the hole exceeds 270mm; you will likely need to use
If you already have a SureFlap Cat Flap, you may be able to re-use your existing adaptors. *Note: The SureFlap Pet Door is a larger variant than the SureFlap Cat Flap and therefore the Pet Door adaptors are not compatible.
For wall installations you will require:
- A Compact Mounting Adaptor; Only when you do not have an existing cut out hole; or if your existing cut out is less than 200 x 200mm.
- If your existing cut out is 200 - 270mm, you will need a Standard Round Mounting Adaptor - This mounting adapter can be drilled and screwed to secure your OnlyCat device to the wall (screws not included)
- If your existing cut out is 270 - 300mm, you will need a Large Round Mounting Adaptor. - This mounting adapter can be drilled and screwed to secure your OnlyCat device to the wall (screws not included). Choose the one which best fits the shape of your space.
Tunnel Extender Guidance
- OnlyCat includes a fixed tunnel depth of 70 mm.
- Each Tunnel Extender adds 50 mm of additional depth.
- Total tunnel depth = 70 mm + (50 mm × number of extenders).
Wall thickness requirements:
- 67–117 mm → 1 Tunnel Extenders
- 117–167 mm → 2 Tunnel Extenders
- 167–217 mm → 3 Tunnel Extenders
- 217–267 mm → 4 Tunnel Extenders
Walls thicker than 267 mm:
For walls exceeding 267 mm, simply continue using the same 50 mm increment logic. Add additional 50 mm tunnel extenders as required until the total tunnel depth meets or slightly exceeds your wall thickness.
If you have any questions, feel free to drop us a message (ideally with some photos) and we'll do our best to guide you.
Updated on: 11/02/2026
Thank you!