2.5Z 40MM Piston RING KIT 2-Stroke 49cc 50cc Motorized bicycle Bike PK16 40mm PISTON KIT 2-Stroke 49/50cc Motorized bicycle Height: 46mm (2") approx. Pin: 10mm (.4") Piston Outer Diameter: 40mm Piston ring Outer Diameter: 40mm, Inner Diameter: 38mm Please check and compare before purchase!!