There is no flexibility in the sole, you can walk on concrete, it seems like these shoes have no lining. I tried them on, ran about 30 seconds, put them back in the box and sent them back, these things are terrible. They look cool but lack functionality. It's a hard plastic that doesn't flex, you can't even wear it there, they don't have any padding, which sucks because the upper feels nice, soft and flexible, good idea, bad execution.