I often get the question, "How do you know what size bobbin to purchase for my machine." My response has been to purchase the bobbin from the manufacturer of your sewing machine. If you 've taken Sewing 1 with me. We've seen various sizes and brands of bobbins in Joann Fabrics.
Well a little internet surfing brought me to Prym/Dritz. Dritz did a wonderful job explaining the difference in a class 15 vs. 66 bobbin. Now the mystery is solved.
Until next time, happy sewing