the only criterion is barefoot length.
if foot is wide, choose bigger size.
CHECK SIZES:
US6.5 =barefoot length 24.1-24.5cm
=EUR size 39
US7 =barefoot length 24.6-25cm
=EUR size 40
US7.5 =barefoot length 25.1-25.5cm
=EUR size 41
US8 =barefoot length 25.6-26cm
=EUR size 42
US8.5 =barefoot length 26.1-26.5cm
=EUR size 43
US9 =barefoot length 26.6-27cm
=EUR size 44
