Superior Threads - Bottomline Prewound Bobbins 118yds each. Approximately 60 percent of the machines on the market are compatible with these standard L size prewound bobbin. The debate continues but the prewound users are winning. Although some machine manufactures warn against using prewound bobbins, it is a fact that many of the educators on their staff do use them. The risk of prewounds is in the thread quality. Make sure you use a good quality thread and clean the bobbin area regularly. The advantage is in saving time and not having to wind your own bobbins. Prewound bobbins hold up to three times more thread than self-wound bobbins.
Most prewound bobbins have cardboard sides which are removable. You need only to remove one side, the side where the sensor light is, and the automatic bobbin sensor will still work. By leaving the other side on, the cardboard side will prevent the bobbin from jumping around as it runs low.
For your peace of mind, if you buy these prewounds and they don't fit your machine, we will buy them back!