For proper fit and size measure the circumference of your head 1" above your eyebrows and around the largest portion of the back of your head.
20 1/2" - 21 1/4" ---------- X-Small
21 1/4" - 22" -------------- Small
22" - 23" ------------------ Medium
23" - 23 3/4" -------------- Large
24" - 24 1/2" -------------- X-Large
24 1/2" - 25 1/4" ---------- XX-Large