I started out with the least expensive bobbin winder and it did not work well at all. I returned it and bought the deluxe version by Simplicity at JoAnn's with a 50% coupon. My Bailey uses Class 15 bobbins and I still had several size L prewound bobbins from the previous machine. The winder works great and I found it helps to put one of those small thread caps for the spindle to keep the prewound bobbin from spinning off the spindle. Also, I use the lowest speed to get the bobbin started. Then I turn it up to the highest speed so that the thread winds more evenly.