Kit 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 gaskets, Domed piston head, Bolt on, It is recommended that Athena's 17.50 mm or 19.00 mm scooter carburetor be used with the bolt on big bore kit. Whenever the cylinder kit is disassembled, replace the gaskets with the specific Athena spare gasket kit, do not use OE replacement gaskets. Can be installed without making any changes to the engine crankcase.