Sizes are in Dutch, Engels and American:

      54 cm       -  6   3/8      -  3  1/2    (also called XS)

      55 cm       -  6   2/4      -  4          (also called S)            

      56 cm       -  6   7/8      -  4  1/2    (also called M)

      57 cm       -  7              -  5          (also called M)

      58 cm       -  7  1/8       -  5  1/2    (also called M)

      59 cm       -  7  1/4       -  6          (also called L)

      60 cm       -  7  3/8       -  6  1/2    (also called XL)

      61 cm       -  7  2/4       -  7           (also called XXL)

      62 cm       -  7  7/8       -  7  ½      (also called XXL)

      It is very important that you measure your head in the right way... like on the image!