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. circumference: M=52-58cm (adolescents aged 9-15 years) 4. Number of ventilation holes on helmet top: 11 5. Regulator system: light and snug, with adjuster knob, it is easy to adjust the size of circumference Inner cushion: The thickened inner cushion belt can be disassembled and cleaned. The inner cushion (cushion cushion) can contact with the to increase comfort. Colour:Blue Material:EPS high density foam + ABS Package Contents: 1 x Ventilation Bicycle Cycling Helmet Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.