The item that I am selling is a great find!  This is a new in the package standard (STD.)  size 66mm Piston Ring Set  (this is a complete ring set for All 4 Pistons!) for the  1973 1974 1975 1976 1977 Z1 and KZ900 motorcycle.   This is a standard size (STD) ring set. .  This has the 2 compression rings and the lower 3pc oil control rings for all 4 pistons, everything to get your pistons/ engine running nicely again.   We only sell the best! This is a top-quality aftermarket item shipped new in the package.  Correct for part # 13008-5005. Good stuff if you are riding or restoring or AHRMA racing one of these cool bikes.  Move over CB750!!  ha...these were and still are fast bikes!