Use the below guide to find the best FlexFit Size for your head. The "Head Size" is measured as the circumference of your head where the hat will sit. 

Hat Size Head Size in Inches Head Size in CM FlexFit Hat Size
6 5/8 21 53 XS
6 3/4 21 1/4 54 XS, S/M
6 7/8 21 3/4 55 XS, S/M
7 22 56 XS, S/M
7 1/8 22 1/2 57 XS, S/M, L/XL
7 1/4 22 3/4 58 S/M, L/XL
7 3/8 23 59 L/XL, XXL
7 1/2 23 1/2 60 L/XL, XXL
7 5/8 24 61 L/XL, XXL
7 3/4 24 3/8 62 XXL
7 7/8 24 7/8 63 XXL
8 25 1/8 64 XXL