This is a new in the package Piston Ring set (1 set for each piston) for the 1974 1975 1976 1977 twin cylinder Kawasaki KZ400 Z400. So this is enough for 1 engine.   These are .50mm (.020") Oversize piston rings. These fit the  stock 2nd oversize Kawasaki pistons.  Correct for part # 13025-5013.  This has the 2 compression rings and the lower 3 pc  oil control ring for both pistons, everything to get your pistons/ engine running nicely again.   Get your old bike up and running again. We only sell the best! This is a top-quality aftermarket item shipped new in the package. Good stuff if you are riding or restoring.