I have an in between head size and recently purchased this in a medium. I had been wearing a Tipperary Windsor in small but was getting frequent headaches with extended wear, tried the medium in that model but it was just too big, so sized up to the medium One K MIPS. I prefer the brushed suede finish on my Windsor, but the matte black finish is nice and doesnt get finger marks so is easy to clean clean. The fit is looser without feeling unsafe, but lacks the custom fit wheel at the base of the skull. The good part is that I can order a small liner and try that to see if leads to a better all round fit. Not too heavy on my head so overall happy with purchase.