Endura airshell road helmet its enduras first foray into the helmet market and early signs are positive ventilation takes place through two systems one internal the other external the large vents visible in the shell are known to endura as clearthru the internal system endura call headstream one they say directs air through the front and out the back of the helmet adjustment proves easy enough with a classic dial mechanism at the rear of the helmet to tighten or loosen the cradle acco