Offering a leading combination of light weight, comfort and cooling performance, the Giro Aeon gives you an advantage every time the road climbs or the heat turns up. Until now, you couldn't get the benefits of lighter weight and better ventilation in a single bicycle helmet. But the advanced Aeon weighs only 222g (Med), yet provides cooling power equivalent to the most ventilated helmets ever made. In addition, it offers the secure fit and luxurious feel of Roc Loc 5, and innovative, thermoformed roll cage reinforcement. If you're looking for the best balance of weight, ventilation and comfort, the Giro Aeon is the new standard. CPSC approved. SM (51-55cm), MD (55cm-59cm) or LG (59-63cm).