I own several Vikings...When I went to a class with Sharon Shaumber she told us the common "L" metal bobbin fits in our machine and works better than the plastic. That would also eliminate the problem of tightening the plastic bobbin when it's wound. The only problem is the "L" bobbin doesn't fit on our winding post, BUT works great on the "sidewinder". Of course the other benefit is that you can but about 100 bobbins for $10!