We use a S/M/L model that covers a range of men's and women's sizes:

Men's
Size US  European CM
XS 5 ~ 5.5 36 ~ 37 22.5cm
SS 6 ~ 6.5 37 ~ 38 23.5cm
S 7 ~ 7.5 38 ~ 39 24.5cm
M 7.5 ~ 8 40 ~ 41 25.5cm
L 9 ~ 9.5 41 ~ 42 26.5cm
LL 10 ~ 10.5 42 ~ 43 27.5cm
XL 11 ~ 11.5 43 ~ 44 28.5cm
XXL 12 ~ 12.5 44 ~ 45 29.5cm
Women's
Size US European CM
XS 6 ~ 6.5 36 ~ 37 22.5cm
SS 7 ~ 7.5 37 ~ 38 23.5cm
S 8 ~ 8.5 38 ~ 39 24.5cm
M 9.5 ~ 10 40 ~ 41 25.5cm
L 10.5 ~ 11 41 ~ 42 26.5cm
LL 11.5 ~ 12 42 ~ 43 27.5cm