Rocker arm assembly for 125cc GY6 QMI152/157 and 150cc GY6 QMJ152/157 engines A rocker arm is a lever that sits on top of the valve stem and opens and closes the inlet and exhaust valves as the camshaft rotatesDescription Rocker arm assembly for 125cc GY6 QMI152/157 and 150cc GY6 QMJ152/157 engines.A rocker arm is a lever that sits on top of the valve stem and opens and closes the inlet and exhaust valves as the camshaft rotates. The rocker arm assembly for 125cc GY6 QMI152/157 and 150cc GY6 QMJ152/157 engines is located inside the cylinder head cover.This rocker arm assembly is used on a wide variety of scooters and ATV brands and models that have Chinese built 125cc GY6 QMI152/157 and 150cc GY6 QMJ152/157 engines. ? WARNING California Residents: Proposition 65 Warning Specifications Parts Included:2 rocker armsCamshaft rocker arm bearings