To ensure a perfect fit, measure the circumference of your head starting in the middle of your forehead and match it with the sizes below: XS 20.10 – 20.50 in (51 – 52 cm) S 20.60 – 21.30 in (52 – 54 cm) M 21.40 – 22.00 in (54 – 56 cm) L 22.10 in – 22.90 in (56-58cm) XL 23.00 – 24.00 in (58 – 61 cm)