The Koso 4V Cylinder Head kit for the Honda Grom and Honda Monkey is the ideal engine part to complete the Koso Big Bore kit. Because of its unique 4 valve design, the air flow and performance are increased. This newly designed head is the perfect addition for those who desire more power and torque. The 4 Valve Cylinder Head Kit features a forged piston, stainless steel 24mm intake valves and 20mm exhaust valves. Feel the speed!