Triple 8 Brainsaver with Sweatsaver Liner Baja Teal Rubber Skate Helmet 21.40 - 22 in (54 - 56 cm) Medium

Brainsaver Rubber Helmet Sizing Chart:

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 - 22.90 in (56 - 58 cm)
XL 23.00 - 24.00 in (58 - 60 cm)