Cylinder KitKit includes complete aluminum cylinder, with a nickel carbide plated bore, cylinder head, piston, rings, 10 mm wrist pin, circlips, carbon reeds and all required top-end gasketsThis cylinder kit can be installed without making any changes to the engine crankcasePiston head is domedBolt onIt is recommended that Athena's 17.50 mm or 19.00 mm scooter carburetor be used with the bolt on big bore kit.Fits '98-'01 BW and Zuma 1 with vertical engine.