This company Step Two Upgrade is out of business but I have NOS (New Old Stock) inventory and am selling it priced to go!
Replacement piston 70cc Big Bore Piston Kit
Includes 45mm Piston, Rings, Pin, Circlips
Pin Size/Diameter: 12mm
Height from Center of Pin to Top: 23mm
Total Height of Piston: 50mm
Ring Height: 1.5mm
Number of Rings: 1