ASME B16.21-2016 pdf download.Nonmetallic Flat Gaskets for Pipe Flanges. This Standard covers types, sizes, materials, dimensions, tolerances, and markings for nonmetallic flat gaskets. These gaskets are dimensionally suitable for use with flanges described in the referenced flange standards. 2 GENERAL 2.1 Relevant Units This Standard states values both in SI (metric) and U.S. Customary units. As an exception, diameter of...