Smith Helmets Size Chart Adult HFS 51 - 55 cm Small 55 - 59 cm Medium 59 - 63 cm Large Junior HFS 48 - 53 cm One Size The Smith Premise Ski and Snowboard Helmet is an audio compatible helmet that fully integrates performance technology into an understated design. The Smartshell On Mold construction method creates a helmet that is lightweight and protective, while adding attention to the cosmetic details never seen before. Smartshell™ construction creates a single-piece injected EPS liner, while traditional In Mold construction requires gluing two pieces together. Smiths AirEvac design maximizes goggle airflow to reduce fogging. The adjustable, easy to use Regulator ventilation system allows you to control the amount of airflow and heat exhaustion, even with a gloved hand. Smiths new Helmet Fit System combines an ultra thin, low profile design, with a specially molded liner to provide a truly custom fit experience. The simple, one button, ""set it and forget it"" design takes up virtually no room, and the ergonomically designed chassis cradles your head. Snapfit™ ear pads are ergonomically designed to be form fitting and comfortable. They are easily removed for washing and effortlessly reinstalled. The premise offers excellent Smith helmet / goggle integration features. The Premise is compatible with Plantronics Bluetooth and Skullcandy Twin-tip audio systems. AirEvac Design Maximizes Goggle Airflow to Reduce Fogging Smartshell On Mold Construction Smith Helmet Fit System to Ensure a Correct and Comfortable Fit Snapfit Ear Pads Regulator Ventilation for Easy Climate Control Plantronics Bluetooth and Skullcandy Twin-tip Audio Compatible ASTM F2040, CE EN 1077 Certified Goggle Helmet Integration: Match Between the Curve of the Goggle and the Brow of the Helmet Goggle Lock Securely Retains the Goggle Strap on the Helmet If you are not sure of your head shape or helmet size, please check out the Helmet Sizing Guide.