ISO 4591:1992 "Plastics, Films and Sheets, Determination of the Average Thickness of Samples and the Average Thickness and Yield of Rolls by Weight Analysis Technique (Weight Method Thickness) " provides a standard method for determining the thickness of Plastic films and sheets. The standard defines the measurement of the average thickness of samples by weight analysis and includes the determination of the average thickness and yield of coils. This method is particularly suitable for situations where mechanical scanning accuracy is insufficient, such as thickness measurement of embossed sheets. This weighted method of thickness determination is able to provide high-precision thickness data, ensuring that Plastic films and sheets meet specifications during production. The second edition of the standard replaces the revised first edition and further refines the measurement technology and application scope.