Differences, where they exist, are shown in Appendix A. This SAE Recommended Practice specifies the general characteristics of piston rings and individual dimensional criteria, which are specified as appropriate in the documents in Section 2. This document also provides a system for coding, designation, and marking of piston rings. This document applies to the manufacture of piston rings up to and including 200 mm diameter for reciprocating internal combustion engines. It also applies to piston rings for compressors working under similar conditions.