Adjustable chin strap Classic clip buckle Interior padding for comfort Scooter and bike approved Australian Standard Certified AS/NZS 2008:2063+A1:2009 Toddler & kids helmets The latest Classic Micro Kids Helmets and are designed for a firm ergonomic fit for the ultimate in safety for scooter, bike and skate riders. Lightweight with inbuilt ventilation the protective helmet is made for comfort on both long and short adventures. Parents can have peace of mind about their kids scooting or cy cl ing both near and far. Available in S and M to protect toddlers and kids with a firm safe fit. For sizing, measure the circumference of the head from the forehead where the helmet will sit, across the furthest point on the back of the head. Please do not guess. [S] Small: 48-53cm [M] Medium: 52-56cm