About the Bontrager Specter WaveCelWaveCel is a revolutionary helmet safety tech that\\\'s available exclusively in these Bontrager helmets. Standard foam helmets are designed to protect against direct impacts. But WaveCel accounts for how most cycling accidents actually happen: ungracefully, with twists, turns and angled impacts. WaveCel is a revolutionary, Bontrager-exclusive helmet technology that\\\'s up to 48x more effective than standard foam helmets in preventing concussions caused by common cycling accidents. Take your protection to the next level. Bontrager Specter WaveCel offers the best in versatility and comfort for everyday rides on roads, trails, gravel and more. From dirt to road, fast or slow, this new wave of protection delivers the confidence you need wherever you ride or race. WaveCel is a collapsible cellular structure that lines the inside of the helmet. This Bontrager-exclusive technology disrupts the safety standards that the industry has accepted for over 30 years. Key Features WaveCel advanced helmet technology BOA® Fit System lets you easily secure and adjust helmet fit with just one hand Fidlock magnetic buckle fastens effortlessly for a quick, secure fit The highly ventilated design offers more airflow to keep you cool Soft, comfortable, moisture-wicking and washable helmet pads Reflective elements on the back of the helmet offer enhanced visibility to be seen Trek Helmet Sizing GuideSmallMediumLargeSize (head circumference)51-57cm54-60cm58-63cm Helmets Buying Guide