This helmet model meets or exceeds both ECE 22.05 and DOT FMVSS-218 motorcycle helmet safety standards. Please Note: Only ECE approved helmets purchased from European importers carry the ECE certification markings. This is due to ECE regulations.ADULT HELMET SIZESX-SMALLSMALLMEDIUM54-55cm 6 3/4-6 7/8 hat 21 1/4″-21 5/8″56-57cm 7-7 1/8 hat 22″-22 7/16″58-59cm 7 1/4-7 3/8 hat 22 13/16″-23 1/4″LARGEX-LARGEXX-LARGE60-61cm 7 1/2-7 5/8 hat 23 5/8″-24″62-63cm 7 3/4-7 7/8 hat 24 3/8″-24 13/16″64-65cm 8-8 1/8 hat 25 3/16″-25 5/8″XXX-LARGEXXXX-LARGE66-67cm 8 1/4-8 3/8 hat 26-26 3/8″68-69cm 8 1/2-8 5/8 hat 26 3/4-27 1/8″YOUTH HELMET SIZESY-SMALLY-MEDIUMY-LARGE53-54cm 6 5/8-6 3/4 hat 20 7/8″-21 1/4″54-55cm 6 3/4-6 7/8 hat 21 1/4″-21 5/8″55-56cm 6 7/8-7 hat 21 5/8″-22″