Outer carbon shell 12K 2 shell sizes 2 dimensions of EPS J.1.E.R. Emergency Cheek Pad Removal System Steel Double D Retention System New Interior Fitting for Greater Comfort Fully Removable and Washable Interiors New Interior Treated with Antibacterial PROTX2 Technology 11 Front Air Intakes and 8 Rear Drains Sizes: Small shell (XS / S / M ) from 53 to 58 cm Large shell (L / XL / XXL ) from 59 to 63 cm To choose the correct size it is necessary to measure the circumference of the head at the height of the temples