Sizing: I'm usually a 10 or 10.5 with thicker socks.  Purchased these in a 10 and they are too short.  As other reviewers have mentioned: the foot moves to the front of the shoe so it then starts slipping in the ankle area with each step.  I also tried these in an 11, which are way too big.  Looks like vionic only makes some 1/2 sizes. Otherwise, comfortable and seemingly well made.