Mountain bike helmet suitable for men sizes 53 57 cm 58 63 cm main colours white blue number of air vents 19 safety features fly net visor with visor size adjustments wheel adjustment system headring features lower edge reinforcement construction in mold weight 260 g inner material polystyrene eps helmet technologies alpina ceramic shell alpina hi eps alpina custom fit alpina run system alpina shield protect alpina ergomatic certified en din 1078