Thread Tension Nut for Singer Industrial Sewing Machine Classes: 16, 17, 24, 31, 44, 52, 69, 71, 78, 95, 96, 132K, 133K, 144W, 145W, 175, 188, 195K, 196K, 240, 241, 245, 251, 260, 261, 269W, 270, 271K, 281, 291, 331K, 366K, 369W, 400W, 402W, 410W, 451K, 457G, 491, 600W, 770, Centurion 121; Consew Classes 18, 28. 30, 118.