US: L/XL to United Kingdom Size 6 7/8
Cross-market women’s hat conversion mapping L/XL specifications into 6 7/8.

Analyzing Hat Size Equivalence Across Markets
US: L/XL: Features a head circumference of 59.5 (23.4 ) measured just above the brow and ears.
United Kingdom Size 6 7/8: Features a head circumference of 56.5 (22.2 ) measured just above the brow and ears.