| Size | Head circum. (IN) |
| XS | 18.8 - 20" |
| S | 20 - 21.6" |
| Size | Head circum. (CM) |
| XS | 48 - 51 cm |
| S | 51 - 55 cm |
K2 Illusion Ski Helmet Sizing Guide for Children
| Size | Head circum. (IN) |
| XS | 18.8 - 20" |
| S | 20 - 21.6" |
| Size | Head circum. (CM) |
| XS | 48 - 51 cm |
| S | 51 - 55 cm |