Lazer O2 Road Cycling Helmet - Unisex The Rollsys retention system allows you to tune the fit with the turn of a wheel on top of the helmet Positioning the dial on top of the helmet rather than in the back makes it ideal for people with ponytails The system surrounds the head completely and supplies a symmetric closure to alleviate pressure points Finished with reflective accents to help enhance your visibility to other road users at any time of day Twenty-four vents sculpted into the In-Mold shell to keep air flowing