Cutex Brand 100 Large Capacity Bobbins for Industrial Sewing Machines #18034 Box of 100 Large Capacity M Size Metal Bobbins For Industrial Sewing Machines Bobbin #18034 Bobbin diameter measures 1" (25.5mm) and 3/8" (10mm) thick The metric measurements on these bobbins are 21mm in diameter and 8.5mm deep. These bobbins have a notch in the center for the bobbin winder. These popular bobbins are also sold under these numbers : DO-DBM(1)N, 117061-001, R1143, 18034, B9117-201-000, MF25B0123, 201143000. (Color of Bobbins May Vary)