Bmx helmet full face bike helmet mountain bike helmet suitable for men sizes 54 56 cm 56 58 cm 58 60 cm 60 61 cm us sizes s m l xl main colour black number of air vents 14 visor with visor size adjustment strap adjustable features chin guard outer material fibreglass weight 1 060 g inner material polystyrene eps marks of approval astm f 1952 en din 1078