Bontrager Specter WaveCel Road Bike Helmet Casque NWT Vice Pink 48x Times more Effective than traditional foam helmets - WaveCel advanced helmet technology - The Boa System lets you easily secure and adjust helmet fit with just one hand - Fidlock magnetic buckle fastens effortlessly for a quick, secure fit - Highly Ventilated - Soft, comfortable, moisture-wicking, and washable helmet pads - Adjustable straps and head retention - Medium with Circumference - 21 1/4 inches - 23 5/8 inches WaveCel is a collapsible cellular structure that lines the inside of the helmet. This Bontrager-exclusive technology disrupts the safety standards the industry has accepted for over 30 years.