Thank you both for your replies. I do have a manual, and I got the 206X13 needles. The bobbin case I got is the one with the cutout. The bobbins that came with the machine are different from any other Singers that I have (and I don't have many different ones). I have a 15 and that one definitely is different. The 306K bobbin is not flat, but is rounded. The middle where it fits on the spindle in the bobbin case is taller than the edges of the bobbin. Does that make sense?