1. Product name: adult and children's outdoor sports and cycling helmets 2. Material: high-density EPS shell ABS external ABS and internal EPS conformal non integrated helmet has the ability to absorb impact and reduce impact force. 3. Head circumference: S=48-56cm (children aged 3-8 years), M=52-58cm (adolescents aged 9-15 years), L=56-61cm (adult men and women) 4. Product weight: single product weight S=281g M=322g L=374g (manual measurement, there will be errors) 5. Number of ventilation holes on helmet top: 11 6. Regulator system: light and snug, with adjuster knob, it is easy to adjust the size of head circumference 7. Inner cushion: The thickened inner cushion belt can be disassembled and cleaned. The inner cushion (cushion cushion) can contact with the head to increase comfort.