Fibre quality has improved appreciably, tenacity norms are higher, and the norms for irregularity of individual fibre properties and the permitted proportion of fibre faults have been reduced but the fibres and yarns now being produced still fail to meet the increasingly stringent specifications imposed by the users. The physico-mechanical indices are not usually a source of complaint but the faster technological processes now in use, notably the high processing speeds, call for fibres and yarns with improved properties so that the light industry demands a still lower proportion of fibre faults.