ISO 8239 specifies the fitting dimensions of needles and needle holders. It defines general terms for sewing machine needles and specifies the tolerances for their fit in the needle holder. In addition to the rangers of dimensions for the nominal shank diameter and the length from butt to eye, ISO 8239 also indicates the preferred combinations of these two dimensions. In order to ensure the interchangeability and to reduce the variety of needles these should serve as a guide when designing new sewing machines and/or sewing machine needles.