But arguably less protection. Some studies have indicated more vents (especially of the style most bike helmets use) may increase rotational injury (since the vents are more prone to "grab"). If we are wearing a helmet for safety, the best kind are usually the "skate-style" helmets with no or few vents. If you aren't concerned about safety enough to go with the more ineffective, and possibly unproductive kind, why wear one at all?