My sewing repair man says "if it came with plastic, do not use metal bobbins", it all has to do with timing, bobbin weight, and other things that I didn't understand, but I do trust him and so only use plastic in my Kenmore. My Pfaff uses metal bobbins. I buy plastic bobbins at Hancock but read the packages that tell me what machines they are for because sometimes they look right, but do not work.
Brenda