Fitted hat
 
Youth 6 1/2 -6 3/4 = 20 1/2 X 21 1/2
S 6 7/8-7 1/8 = 21 3/4 x 22 3/8
M 7 1/8 -7 3/8 =22 3/8 x 23 1/4
L 7 3/8-7 5/8 = 23 1/4 x 24
XL 7 5/8-8 = 24 x 25 1/4