The FeatherWeight features In-Mold technology to make a custom shape and fit utilizing a thin outer shell that covers and protects high-density EPS foam. - High density EPS in-mold construction - Tested and certified for CPSC and EN 1078 standards for bicycle use - Two sets of padding included for custom fitting - Crow rivets and 10 flow-vents to keep cool - Small/Medium = 50 - 56cm - Large/X-Large = 58 - 61cm