I have a 758 that I use all the time. The original bobbins that came with my machine work great. If you purchase new bobbins they will not wind properly, including the ones I bought that were Singer. The plastic is not as heavy on them as the original ones. The bobbins with the white bottom won't wind properly either. However, I can sew with both of them if I wind them by hand. Make sure there is no lint in there and oil the channel. If the bobbin case is not in right it won't work either.