Bobbin case for Singer 31-15, 44-10, 331K Industrial Sewing Machines. This high quality bobbin case fits following machines : Singer : 31 Class (except 31-19, 31-20), 31-15, 44-10, 44-12, 331K, 431D Adler : 37 Alfa : 157 Consew : 30 Necchi : 500, 510, 512, 513, 514, 515, 520, 522, 523, 524, 525, 527, 529, 532, 534, 539, 554, 600, 601, 602, 603 Set of 2, high quality bobbin cases for Industrial Sewing Machines. Singer 31 Class, 31-15 & Consew 30.