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 suitable for the following machines: 
For all BERNINA Activa and 3 Series machines
BERNINA Virtuosa
BERNINA Aurora
BERNINA Artista 165, 170 and 630
BERNINA 555 and 570
And is suitable for most Legacy machines