I eschewed Nicks's sizing advice and sized down only 1/2 length as on my lace-up Nicks instead of a full size. Fit is excellent with only nominal heel slip, even on the very first wear. My instep is slightly higher than normal so don't follow my lead if you consider your feet to be low-volume. It's unknown if my sizing advice would hold for a 55 last pull-on as the high arch tends to shorten the foot.
