Originally Posted by ktbb

As several have said, I'd stick with what came with your machine....except that I also use the cardboard prewound bobbins...but not all machines can handle them.

One disadvantage I know about for plastic bobbins is that you should use use slow speeds and lots of caution when winding metallic or other stretchy threads on the plastic bobbins since the threads can relax once on the bobbin and actually make the plastic bobbins warp from the pressure on the inner core...because of this pressure, they may not rotate correctly. One hint I've heard for checking for warped plastic bobbins (and works for wrong sized bobbins as well) is that if it won't fit snugly and easily on your bobbin winder post, it probably shouldn't be used on your machine.