Scooter Big Bore 150cc to 170cc Cylinder Head Gy6 157qmj Performance Exhaust #99004 Overall Height (cylinder) is 90mm High Performance Variator Set with copper Rollers - 14g No Rev Limit Performance CDI, 2 plug 6 pin, 38mm*74mm*30mm Head comes with performance springs, retainers and keepers intake valve is 27mm, exhaust is 23mm