I just ordered the Medium. Prior to ordering the medium I measured my head and it was exactly 58cm. Exactly. Fattest part of my head = 58 cm. The medium came, the medium did not fit. The problem, my head was a little too long (forehead to occiput). Had it been a little more circular rather that oval, the size would have been grand. However, I literally could not get the helmet on my head all the way.
I did not use the helmet on the road, I think it was beautiful. I'm sad there are no larges in stock. Hope that helps someone else out there.
They made me rate it. So four stars for looking rad, and potentially comfortable. -1 star for not fitting my head.