Establishes the flatness, permissible deviations for thicknesses and physical properties of flat thermosetting polyester laminated glass mat sheets. Specifies three types of sheet, intended for mechanical and electrical applications. The thicknesses are in the range from 1.6 mm to 25 mm. Does not specify requirements for thermal endurance. Covers definition, classification, permissible deviations for thicknesses and physical properties. Includes several appendices.