Here is a chart of the liner size for each size helmet. The liners are only interchangeable within the same shell size.
| Helmet Size | Liner Size | Shell Size |
|---|---|---|
| XS | 12 mm | Med |
| Small | 10 mm | Med |
| Medium | 8 mm | Med |
| Large | 10 mm | Large |
| XL | 10 mm | 2XL |
| XXL | 8 mm | 2XL |
| 3XL | 12 mm | 4XL |
| 4XL | 10 mm | 4XL |