Kids helmet mountain bike helmet suitable for boys sizes 47 52 cm 52 57 cm us sizes s m main colour white surface shiny number of air vents 17 safety features fly net chin padding chin pad not inlcuded inner padding removable visor with visor size adjustments wheel adjustment system headring construction in mold weight 220 g inner material polystyrene eps helmet technologies alpina ceramic shell alpina hi eps alpina run system alpina ergomati