i don't know, but the more yellow owl socks i get, the more i want! cute, colorful, cheerful, soft. i have long narrow feet (women's 10.5+) and the large socks fit well, *almost* too long but with the heel situated they're fine. i also own YO socks in the previous women's OS that are now labeled small and those fit too, but tighter/shorter so even if i love the design i'm probably gonna stick with larges from now on.