Protection Lightweight in-mold construction fuses the exterior shell and EPS foam for a one-piece design that's lightweight and durable Zonal KOROYD® coverage for lightweight, energy-absorbing and ventilated impact protection Mips® Brain Protection System reduces rotational forces caused by angled impacts to the head Certification: ASTM F 2040, CE EN 1077:2007 CLASS B Fit / Integration Designed for ultimate integration with Smith goggles for maximum comfort and venting AirEvac ventilation system integrates with Smith goggles for fog-free lenses Micro-adjustable dial fit system for easy, on-the-go size adjustment Features Eight fixed vents for consistent airflow Magnetic chin strap buckle makes for easy one-hand operation Aleck® audio systems compatible Removable Snapfit SL2 ear pads add warmth and are audio-chip compatible Removable goggle strap lock for streamlined shell when goggles are worn under helmet Beanie compatible ADULT SNOW HELMETS Size Head Circumference S 51-55cm Round Contour Fit S 55-59cm M 55-59cm Round Contour Fit M 59-63cm L 59-63cm Race L 59-61cm Vida L 59-61cm Round Contour Fit L 63-67cm XL 63-67cm https://www.youtube.com/watch?v=_jPb0qoog7c