Even after measuring per the instructions, these are about a half inch too long, creating a gap at the heel.  Would be better to go a size down and have it fit like a glove.  You don't want or need extra space, especially in the toes (no toe box like a shoe) where you want your toes all the way forward and filling the toe sleeves.

They are very comfortable, and definitely give your feet a bit of a workout.  Interesting feeling on the toes.  Went for a 1.5 mile walk and liked it, but will take some getting used to.  They are hard on the heels, since there is no padding at all.  I am sure calluses will develop over time if you follow their break-in plan.