Size Head Circumference (inches) Head Circumference (centimetres) XS/S 20.5 - 22" 51 - 54cm S/M 21.3 - 22.8" 53 - 57cm L/XL 22.8 - 24.4" 57 - 60cm Breakthrough technology that delivers the deepest fit with unlimited customization for supreme comfort and security. It starts with Pro-Tec's most advanced and slimmest-profile shell design, wrapped with newly designed luxurious liners to hug your head like you’ve never experienced before. The LOW PRO is a true helmet revelation - and it’s fully certified for: U.S. CPSC Safety Standard for Bicycle Helmets for Persons Age 5 and Older. ASTM F1447 – Standard Specification for Helmets Used in Recreational Bicycling or Roller Skating. ASTM F1492 – Standard Specification for Helmets Used in Skateboarding and Trick Roller Skating.
