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# What accessories do I require for installation?

## Start with the current installation guide
For a wall installation, the [current OnlyCat wall guide](https://www.onlycat.com/installation-guide-walls/) recommends a **Compact Mounting Adaptor** and **tunnel extenders to suit the wall thickness**. For a larger existing opening, confirm the appropriate adaptor using the measured opening, material, thickness and clearance before ordering or cutting. The current website guide takes precedence over older size examples below.

**Does a cat push the flap?** Yes. OnlyCat has a push door; it is not motorised. The locking mechanism controls access, and the cat pushes the door when access is allowed.

| Door Installations

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;](https://www.onlycat.com/store/tunnel-adaptor-50mm/)
* If your door is between than 60 and 90mm thick you may require [100 mm screws](https://www.onlycat.com/store/long-10cm-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:
* A [Standard Round Mounting Adaptor](https://www.onlycat.com/store/glass-mounting-adaptor/).

![](https://storage.crisp.chat/users/helpdesk/website/-/9/d/9/a/9d9a00682326c00/standard-mounting-adapter_t60z85.webp =125xauto)
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](https://www.onlycat.com/store/glass-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.


![](https://storage.crisp.chat/users/helpdesk/website/-/9/d/9/a/9d9a00682326c00/large-mounting-adapters_1irjup.webp =525xauto)
||| Glass Installations


For installations in glass (212 - 270 mm diameter) you will likely need:
* A [Standard Round Mounting Adaptor](https://www.onlycat.com/store/glass-mounting-adaptor/)\*

If the diameter of the hole exceeds 270mm; you will likely need to use
* A [Large Round Mounting Adaptor.](https://www.onlycat.com/store/glass-mounting-adaptor/)

\*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.*

|| Wall Installations

For wall installations you will require:
* A [Compact Mounting Adaptor](https://www.onlycat.com/store/glass-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](https://www.onlycat.com/store/glass-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.](https://www.onlycat.com/store/glass-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](https://www.onlycat.com/store/tunnel-adaptor-50mm/)
* **117–167 mm** → 2 [Tunnel Extenders](https://www.onlycat.com/store/tunnel-adaptor-50mm/)
* **167–217 mm** → 3 [Tunnel Extenders](https://www.onlycat.com/store/tunnel-adaptor-50mm/)
* **217–267 mm** → 4 [Tunnel Extenders](https://www.onlycat.com/store/tunnel-adaptor-50mm/)

**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.
![](https://storage.crisp.chat/users/helpdesk/website/-/9/d/9/a/9d9a00682326c00/tunnel-calculator_b69vwq.webp =903xauto)

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.
## Confirm the right accessory before ordering or cutting
Use the current website [door](https://www.onlycat.com/installation-guide-doors/), [glass](https://www.onlycat.com/installation-guide-glass/) or [wall](https://www.onlycat.com/installation-guide-walls/) guide for the installation you are planning. The website is authoritative if an older size example here differs.
For an existing opening, send Support its measured width and height (or diameter if circular), the door or wall thickness, material, and photos showing clearance on both sides. We can confirm the adaptor for your particular opening. The current glass guide specifies a 212 mm diameter for a new opening and describes adaptors covering existing openings up to 300 mm. Larger or unusual openings need individual confirmation.
If there is metal inside the door, ask before cutting or enlarging the opening; do not assume a magnet will detect aluminium. Never cut or drill the OnlyCat tunnel, which contains the microchip antenna. Use the dedicated [cable routing article](https://help.onlycat.com/en/article/what-is-the-best-way-to-route-the-power-cable-pfnqa4/) when planning power.