Priced and sold per package of 5 bobbins. Each BERNINA sewing machine has a special hook for bobbins and bobbin cases, and the CB Hook is used in particular for sewing utility and decorative stitches with a stitch width of up to 5.5 mm. CB-hook Bobbins and Bobbin Cases are required for the following machines: all BERNINA activa and 3 Series machines; BERNINA virtuosa; BERNINA aurora; BERNINA artista 165, 170 and 630; and BERNINA 555 and 570.