Metric
| Size | Head Circumference (cm) |
| S | 53 - 55 |
| M | 55 - 57 |
| L | 57 - 59 |
| XL | 59 - 61 |
Imperial
| Size | Head Circumference (in) |
| S | 20.87" - 21.65" |
| M | 21.65" - 22.44" |
| L | 22.44" - 23.23" |
| XL | 23.23" - 24.02" |
Tempish Wruth Guide to Sizing Adjustable Helmets
Metric
| Size | Head Circumference (cm) |
| S | 53 - 55 |
| M | 55 - 57 |
| L | 57 - 59 |
| XL | 59 - 61 |
Imperial
| Size | Head Circumference (in) |
| S | 20.87" - 21.65" |
| M | 21.65" - 22.44" |
| L | 22.44" - 23.23" |
| XL | 23.23" - 24.02" |