I ordered a 5M. I have a short, wide foot. Ideally I wear a 5W, which is almost impossible to find in any brand. So often times I will size up to a 5.5M, 5.5W, or even 6M, to accommodate my wide foot. Not with these shoes! DEFINITELY SIZE DOWN!!! Not only is the 5M a little long, it is very wide. If 4M was an option, I would be exchanging it. I am glad it had 3 adjustable/Velcro straps as they are adjusted as small as they go and I STILL have more room. That never happens; it is usually the other way around! This is my first pair of Vionics, and I am not sure about the high arch orthodic. I am hoping I will grow to love it!