This is a new in the package Piston Ring set (1 set for each piston..so this is enough rings to do all 4 pistons) for all years and models:  1983 1984 1985 Nighthawk CB650 CB650SC Four Cylinder.   This set is also correct for the 1 years only 1983 CB550 SC Nighthawk.  This is a standard size (STD) ring set.  #13011-ME5-004.  This has the 2 compression rings and the 3 pc  lower oil control rings for all 4  pistons,  everything to get your pistons/ engine running nicely again with proper compression.  These are for stock Standard STD. bore size 60mm.  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 your CB650.  That is it!  If you may have an earlier year CB650... 1979-1982..these model years take a different ring set size..we do stock that rings set too..so just search in our store for that item.   If you may need new gasket set or clutch, we have those too. We look forward to doing business with you.