Small/Medium (52cm-60cm) Product Features Adjustable Spin Dial allows for perfect fit and three sets of removable low-density polyurethane foam insert liners for comfort, and for refining fit. Anti-Pinch, Magnetic Buckle/chinstrap for one-handed operation. 360 degree Reflectivity in front, back and side Nutcase logos. Complies with CPSC standard for age 5 + up - Injection-molded ABS shell- Expanded Polystyrene (EPS) protective inner foam for high impact protection. 2 Front intake vents, 7 multiple top-mounted exhaust vents, and 2 Rear exhaust vents.