Nike Hat Sizing
Men's S/M M/L L/XL One Size Fits All
Numeric Size (in.) 6 3/4 - 7 1/8 7 - 7 3/8 7 1/4 - 7 5/8 6 3/4 - 7 5/8
Head Size (in.) 21 1/4 - 22 3/8 22 - 23 1/8 22 3/4 - 23 7/8 21 1/4 - 23 7/8
Head Size (cm) 54 - 57 56 - 59 58 - 61 54 - 61