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 applications. It covers dimensional interchangeability only and does not involve design characteristics of the item except where specified, nor does it involve physical or chemical characteristics of the material used. It does not cover glass stopcocks with glass plugs (Note 2) or stopcocks intended for use in high-vacuum work.