Adults: fits 58 - 63 cm, 22.8 - 24.8 inches head circumference; Breathable structure: air holes for ventilation and heat dissipation; Adjustment spin dial and strap to insure the perfect fit; Helmet pads with shock absorbent material; Securely close the helmet by usage of the buckle and straps; Light weight for comfort and easy usage Soft fabric liner for ultimate comfort, detachable and washable for your convenience