Protection, airflow, fit and comfort are what makes a road bike helmet exceptional. Many road helmets now feature MIPS technology which adds a further layer of protection by reducing rotational impact forces. Road helmets are more aerodynamic, thus creating the "semi" aero helmet that reduces drag without limiting comfort or visibility. A micro adjustable retention system allows just right fit and adjustment on the fly. The number of vents in a helmet is important if you ride in very hot conditions.