the only criterion is barefoot length.
if foot is wide, choose bigger size.
CHECK SIZES:
US4.5 =barefoot length 22.1-22.5cm
=EUR size 35
US5 =barefoot length 22.6-23cm
=EUR size 36
US5.5 =barefoot length 23.1-23.5cm
=EUR size 37
US6 =barefoot length 23.6-24cm
=EUR size 38
US6.5 =barefoot length 24.1-24.5cm
=EUR size 39
US7 =barefoot length 24.6-25cm
=EUR size 40
