Marked size Euro 41.
I believe this is a 10 US womens size. However the boot is marked 11B US, which is a more narrow foot. So if your not as narrow I would think 10 would be more accurate. CNN size is 255 (1.5) I believe this is US 10.
So overall I would say this is a 9.5 to 10 to 10.5 size. Unless your foot is narrow in which an 11 might fit. The more wide your foot, go with the 9.5 size.