BERNINA 034320.70.00 Bobbinwork 7 Series Red Bobbin Case, Sewing Upside Down has never been sew much fun.

Second Bobbin Case. Many sewing machine manufactures make a speciality bobbin case for bobbinwork. These bobbin cases are not the same bobbin case that came with the sewing machine. They usually are a different color and have a longer screw to adjust the tension setting depending on the thickness of thread. It is NOT recommended to adjust the bobbin case tension of the bobbin case that came with the machine. That bobbin case has been correctly set for sewing thread. Leave it be.