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 5/8" - 22".........Small
22 1/2" - 22 7/8".....Medium
23 1/4" - 23 5/8".....Large
24" - 24 3/8".........X-Large
24 3/4" - 25 1/4".....XX-Large