Specifies the revision number of the piping materials class. If you have enabled the Piping Spec Version Management Option in the Model Options node in Catalog or the Default Project Options sheet, the text that you enter here is appended to the end of the piping specification name. For example, if the piping specification is originally named 1C0100, the piping specification with the revision is named "1C0100, Rev: <text>". You must change this revision number manually each time you make a change to a piping specification.