I'm a size 11 and I got an 11.5 and they fit me fine, at first I wore them casually at first, then I switch to strapping'em up and ball in them.
EDIT: I would not recommend balling in them, if your a sg/sf under 140 lbs, they feel heavy and have a "blocky" feeling, I felt very high off thecourt when I balled in mine. So I just use mine a beaters and lift weights in them