This document specifies the dimensions, types, designation and marking of non-metallic flat gaskets, with or without inserts, for flanges in accordance with EN 1759-1, EN 1759-3 and EN 1759-4, for Class 150, Class 300, Class 600 and Class 900 for nominal sizes DN 15 to DN 600. In addition, this document also gives guidance on typical materials used and how they should be marked.