LS2 Helmet Sizing

Manufacturer's Suggested Size Chart (Not a guarantee of fit) 
Size Centimeters  Inches
2XS 51 - 52 20.08 - 20.47
XS 53 - 54 20.87 - 21.26
SM 55 - 56 21.65 - 22.05
MD 57 - 58 22.44 - 22.83
LG 59 - 60 23.23 - 23.62
XL 61 - 62 24.02 - 24.41
2XL 63 - 64 24.80 - 25.20
3XL 65 - 66