Beneath the sleek silhouette, you&';ll find the adjustability of an In Form fit system, Thermostat Control adjustable venting and compatibility with aftermarket audio systems. Hard Shell construction: EPS foam liner Compatible with aftermarket Giro audio systems by Outdoor Tech Fit System - easy to dial in a custom fit in seconds, even with gloves on. Ergo-friendly dial at the base of the helmet that provides up to 6cm of adjustment and enhanced stability Seamless Compatibility with all Giro goggles: Seamless Compatibility with all Giro goggles Hard Shell construction produces great helmets at a great value. A rugged outer shell is molded and then attached to the EPS foam liner. Thermostat Control adjustable venting - allows custom-tuning of airflow instantly with a simple, low-profile control button on the outside of the helmet Stack Vent Technology"