1 Piece PFAFF 783, 784, 786, 4760 SERGER UPPER MOVING KNIFE PART#340406 Replacement UPPER MOVING KNIFE for the PFAFF 783, 784, 786, 4760 home serger sewing machine. This upper knife fits on : Pfaff models: 774, 776, 785, 787, 788 National N50E, JcPenney 928, Mammylock ML1026, Necchi PL1020, PL1026, PL1036, Nelco S928D, Supreme 928A, 928AT This also fits the following models. J.C. PENNY SERGER MODELS - 928. MAMMYLOCK SERGER MODELS - ML1026, PL1026. NATIONAL SERGER MODELS - N30, N40, N50, N50E. PFAFF SERGER MODELS - 774, 776, 783, 784, 785, 786, 787, 788. NELCO (SUPREME) SERGER MODELS - S928D.