I made the small size and used smaller needles than specified but it's still pretty big: I could have made the XS instead. Close-up of the stitch:
And the finished item, which looks much better on me.
This is the first time I've knitted a band in one piece using a circular needle. I didn't enjoy doing it but it does give a neat finish. People who love circular needles: how do you cope with having all your work hanging off two needles? This kept my knees warm but it's inconvenient to store and impossible to carry around with you.
Now is just the weather for it, phew!