Hat size question

[deadmystery.livejournal.com]

Hello! In my desperate quest to find a hat that doesn't require DPNs that I don't have and can't find locally, I came across a pattern that I think would be really neat. And, I don't have to buy anything new to make it. =)

http://www.mlminspirations.com/patterns/FlowerHat/hat1.html

However the pattern does not tell me what size head an Adult Small or Adult Large will fit. Has anyone made this, and can tell me? Or can you tell from the pattern? I'm sorry if I should be able to tell and am missing something, I still consider myself a novice knitter. I appreciate your help!

EDIT: Well, I am thinking from the gauge that the small size is about 20.5 inches. And ribbing stretches a lot, doesn't it? So it will fit a 22" head, yes? Thanks~