Bell Trail Boss The Super Air is the first trail helmet to offer Spherical Technology(TM), making it our most advanced trail helmet. Period. Spherical Technology&';s Ball-and-Socket design, powered by MIPSA(R), helps redirect impact forces away from the brain by allowing the outer liner to rotate around the inner liner during a crash.This combination of outstanding safety, optimized ventilation, and extreme lightness brings epic achievements within reach-on any trail, in any terrain. When you&';re ready to step up, upgrade by adding the optional chin bar. See you on the trail! FEATURES CIRCUMFERENCE - 52-56 CM FUSION IN-MOLD POLYCARBONATE SHELL PROGRESSIVE LAYERING(TM) ADJUSTABLE VISOR COUNTRY OF ORIGIN - CHINA OVERBROW VENTILATION(TM) FLOAT FIT(TM) PRODUCT WEIGHT 410G (SIZE M) CERTIFICATION COMPLIES WITH THE US CPSC SAFETY STANDARD FOR BICYCLE HELMET FOR PERSONS AGE 5 AND OLDER