Triple Eight Standard Liner Helmet has been a favorite of athletes and in the action sports industry in general since 1994. With a classic design, our helmet is designed for skateboarding and roller skating. Triple Eight Standard Liner Helmet is available in four sizes: S 20. 60 in – 21. 30 in (52-54cm) M 21. 40 in – 22. 00 in (54-56cm) L 22. 10 in – 22. 90 in (56-58cm) XL 23. 00 in – 24. 00 in (58-60cm) To determine proper size, measure with a soft tape measure or string. This product is NON-CERTIFIED and is NOT intended for use as a bicycle helmet. This product has NOT been tested under CPSC, ASTM, or CE safety standards.