Applicable to spun single and folded yarns of any fibre or mixture of fibres manufactured by any spinning systems. Not recommended for testing filament yarns, glass yarns, more complex structures such as cabled yarns or cords. Not applicable to those yarns having a diameter so great as to prevent the winding of the skein in two even layers. - Replaces the first edition (ISO 6939:1982) and constitutes its minor revision.