This Standard Practice establishes recommended rules and guidelines for determining metric units and numbers@ when needed@ for use in MSS valve@ flange@ fitting@ and actuator Standard Practices. PURPOSE This Standard Practice provides recommended rules and guidelines to be followed by MSS Technical Committees while developing or revising Standard Practices or other documents in which there is a need to use both U.S. Customary and metric units. This Standard Practice may also benefit end-users of MSS standards and other interested parties. Where both units are included@ the standards developing group determines the order in which they are presented. When used@ the alternate units shall be either: a) In textual references@ immediately following the preferred unit in the text and be separated by parentheses or; b) In tabular references@ included in separate columns or presented at the end of the document in the form of an annex.