1.1 This specification covers standard dimensional requirements for obtaining, within practical limits, interchangeability in glass stopcocks (Note 1) with polytetrafluoroethylene (PTFE) plugs for ordinary laboratory and industrial applicat This specification covers dimensional interchangeability requirements of glass stopcocks with polytetrafluoroethylene (PTFE) plugs for use in ordinary laboratory and industrial applications. However, it does not cover the design characteristics of the