SPECS: S: 51-55 cm M: 55-59 cm L: 59-63 cm XL: 63-67 cm We recommend you try helmets on before buying. Make sure the helmet fits with a little room when the fit system is loose, and sits low enough to protect your forehead without hindering vision. Once you've got the right size, you can adjust the fit. DESIGN & TECHNOLOGY: Intended for adult wear Designed for all-season use Built for use on the slopes and at the skate park Self-adjusting lifestyle fit system flexes to match your head shape for ultimate comfort Bombshell construction delivers injection-molded ABS for ultimate durability and ding resistance AirEvac(TM) ventilation system funnels warm air out through internal channels in the helmet liner and external vents, providing continual airflow and breathability AirEvac(TM) ventilation system integrates with Smith goggles for fog-free lenses Designed for ultimate integration with Smith goggles for maximum comfort and venting Airflow Climate Control with 14 vents delivers strategically placed vents to expel warm air while minimizing drafts Bombshell Ear Pads for form-fitting comfort Removable goggle strap lock for streamlined shell when goggles are worn under the helmet Compatible with Outdoor Tech(TM) Audio Systems Weight (Size M): 19 oz / 550 g Certification: ASTM F 2040, CE EN 1077:2007 Class B, CPSC, CE EN 1088 Manufacturer's lifetime warranty