> For the complete documentation index, see [llms.txt](https://docs.anthriq.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.anthriq.com/bxi-studio/configure/head-size.md).

# Select head size (Instinct)

<figure><img src="https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2FrZPKEKCuinrnsLbWC3Y5%2FInstinct%20Headsize2.png?alt=media&amp;token=00cdb5f9-4adc-42be-a55d-796f3d9c153c" alt=""><figcaption></figcaption></figure>

The head size selection screen pre-positions the headset's motors to match the subject's head circumference. Fine-tuning happens later in [Electrode Configuration](/bxi-studio/configure/electrode-config.md).

## Available sizes

| Size | Label       | Circumference |
| ---- | ----------- | ------------- |
| XS   | Extra Small | 50–52 cm      |
| S    | Small       | 52–54 cm      |
| M    | Medium      | 54–56 cm      |
| L    | Large       | 56–58 cm      |
| XL   | Extra Large | 58–60 cm      |

Medium is selected by default.

## Set the size

1. Click the pill matching the subject's measured size.
2. Click **Continue** to start the motor adjustment.
3. BXI Studio moves all 15 motors to their preset positions for that size.
4. A progress indicator shows the adjustment is in progress.
5. Once complete, the button changes to **Next**.
6. Click **Next** to proceed to [Wear Headset](/bxi-studio/configure/wear-headset.md).

## Motor adjustment

When you click Continue, the headset physically adjusts all electrode positions. This takes 5–15 seconds. During adjustment:

* The Continue button is disabled.
* The Skip and Back buttons are dimmed.
* A loading state is shown.

> **Warning:** Do not put on the headset during motor adjustment. Wait for the **Next** button to appear before fitting the headset.

## Measure head size

Click **Need help choosing head size?** to open a guide with measurement instructions. Use a soft tape measure around the widest part of the head: above the eyebrows and around the back, just above the occipital bone.