Grivel Stealth Helmet

Perhaps most notable is the Stealth’s unusual look. It isn’t a smooth bucket; rather, the shell is a geodome of angles. These reportedly act as buttresses, adding rigidity without weight. Whether the design increases protection I can’t say, but you can sit on the helmet, and, despite being Swiss-cheesed with ventilation slots, the Stealth has impressive side-to-side and front-to-back rigidity.