Description Genuine Cummins OEM piston ring set 4309257 for QSB6.7 marine diesel engines, used in base engine rebuilds and overhauls. Cross References/Supersedes: Not specified Restores proper cylinder sealing, compression, and oil control on Cummins QSB6.7 marine engines. Used when replacing worn or damaged piston rings during QSB6.7 marine engine service. Direct replacement for Cummins part number 4309257 to maintain OEM performance and reliability.