Mountain bike helmet suitable for men sizes 51 56 cm 55 59 cm 58 63 cm main colours red black white number of air vents 17 safety features fly net visor with visor size adjustments wheel adjustment system headring features lower edge reinforcement construction in mold weight 240 g inner material polystyrene eps helmet technologies alpina ceramic shell alpina custom fit alpina run system ergo alpina edge protect alpina shield protect