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.
21 1/4" - 21 5/8"------- X-Small
21 5/8" - 22"---------- Small
22 3/8" - 22 3/4"------- Medium
22 3/4" - 23 1/4"------- Large
23 3/8" - 24"----------- X-Large
24 1/2" - 24 3/8" ------ XX-Large