My noggin is barely 22 inches around; that is, it would be expected to have ample room in a "medium" hat size, and so I might assume that a one-size hat would be expected to fit me, if it's at all expected to fit the average customer. And I practically got a headache just trying these on for a minute when they arrived. I will risk undermining the credibility of my review by admitting I didn't originally try to figure out what the hell the "13*22cm...can stretch to 32cm" advertised is supposed to mean. I naïvely imagined that it must mean it fits a variety of average people. And I am average, right? I'm a medium! Well, it turns out 22x13cm is the dimensions when laid flat. Pretty useful, since heads are also like pancakes. So to measure if that will fit you, all you have to do is flatten your head and lay it on the table and stretch a tape measure along its spread out width. Silly customer I am, I didn't think to do that. Ok, ok, also you could measure your head circumference and divide it in half. Again, I did neither of these things. I am a medium. I felt entitled. I, foolishly, erred on the side of being reasonable and projecting that reasonableness onto hat vendors. Anyway, I'm not done doing math yet. So, dividing my head circumference (22in = 56cm) by pi, Pancake Me is just shy of 18cm wide. Shouldn't that make 22cm-32cm too big for me, not too small? Maybe I suck at math, because this just doesn't add up. Fortunately, I also suck at running, so when I'm out there in the Seattle rain trying to insulate my bald head, I just might not be able to go long and far enough to truly appreciate the medieval torture helmet features of these elastic bands. Once again, as this goes to show, you just don't expect the Spanish Inquisition.