scope:

This International Standard specifies a "cross-section method", ¹ for determining the average diameter, i.e. the average value of the actual diameters (real diameters), of fibres in a textile glass staple fibre yarn or of filaments in a textile glass continuous filament yarn. These diameters must not be mistaken for the nominal diameter, which is defined as the diameter used for the designation of textile glass products and which corresponds approximately to the mean real diameter of the filaments or staple fibres, expressed in micrometers and rounded to a whole number (ISO 6355).