Standard 9:1 compression ratio. Perfect for a stock rebuild. Piston includes the wristpin and wristpin clips. Note: Piston rings must be purchased separately. Note: In any and all applications the technician must be able to judge components for their suitability in combination with the other engine components, prior to installation. It is of importance that a knowledgeable mechanic will install & make adjustments as required. The rider must follow standard break-in and riding procedures for overhauled engines.