Measuring your head with a fabric tape measure around the circumference of your head holding the tape just above your eyebrows and ears. 1" = 25mm

SE4 Carbon and Composite Helmet Size Chart
Head circumference Inches 21 1/4 21 5/8 22 22 3/8 22 3/4 23 1/4 23 5/8 24 24 3/8 24 1/17
Hat 6 3/4 6 7/8 7 7 1/8 7 1/4 7 3/8 7 1/2 7 5/8 7 3/4 7 7/8
CM 54 55 56 57 58 59 60 61 62 63
SE4 Carbon/Composite XS
S M
L XL XXL
Helmet Size  YM YL XS SM MD LG XL 2X
Headliner Thickness 17mm 13mm 17mm 13mm 17mm 13mm 17mm 13mm
Cheekpad Thickness 38mm 28mm 28mm 23mm 38mm 28mm 33mm 25mm
*Headliners can be interchanged within the same EPS size.