This document specifies the essential dimensional features of rectangular rings made of cast iron, Types R, B, BA and M, having diameters up to and including 200 mm, used in reciprocating internal combustion piston engines. It is also applicable to piston rings of compressors working under similar conditions.Cross References:ISO 6621-4ISO 1101ISO 6621-1ISO 6621-2ISO 6621-3ISO 6621-5ISO 6623ISO 6624-1ISO 6624-2ISO 6624-3ISO 6624-4ISO 6625ISO 6626ISO 6626-2ISO 6627