Size Guide for Aegis Helmet
How to Measure Your Head
Use a tape measure starting at the hairline on your forehead, around the back of your head at the highest point, and then down about 2 cm below the bump at the back of your head. Wrap it around your head, adding 2 cm for tolerance.

Size Recommendation
S: Suitable for Head Circumference 51-54cm
M: Suitable for Head Circumference 55-58cm
L: Suitable for Head Circumference 59-61cm