Mountain bike helmet suitable for men sizes 52 57 cm 57 62 cm 59 64 cm main colours green black white number of air vents 25 safety features fly net visor with visor size adjustments wheel adjustment system headring features lower edge reinforcement construction in mold weight 250 g inner material polystyrene eps helmet technologies alpina ceramic shell alpina hi eps alpina custom fit alpina run system ergo alpina edge protect alpina shield protec