La Sportiva's recommendation: "Buying tips: same sizing as Cobra (1/2 size smaller than other more structured La Sportiva models), Python will take longer to adapt to the foot, it will also maintain its shape and features over time." http://www.lasportiva.com/magazine/?p=1176&lang=en Works good for me. I wear the Miura VS in 42 and the Python in 41,5
relation between Miura VS and Python size