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 1/8" - 21 1/2" -------- X-Small
21 1/4" - 22 1/8" -------- Small
22 3/8" - 23 1/8" -------- Medium
23 1/4" - 23 3/4" -------- Large
23 7/8" - 24 3/4" -------- X-Large
24 7/8" - 25 3/4" -------- XX-Large