Use a flexible tape to measure the circumference of the head at the largest point (usually around 25mm above the ears.) Round up if between sizes.
| Helmet Size | CM |
 |
| 00 | 51 | |
| 0 | 52 | |
| 1 | 53-55 | |
| 2 | 56-57 | |
| 3 | 58-59 | |
| 4 | 60-61 | |
| 5 | 62-63 | |
| 6 | 64 | |
| Hybrid XL Helmet | ||
| 7 | 65-66 | |
| 8 | 67-68 | |