Originally Posted by quilttiger

I love and have used prewound bobbins (size L from Superior Threads) for both sewing on my DSM and FMG on my previous shortarm. However, my new Bailey machine uses Class 15 bobbins. I have tried size L prewounds with mixed success. I got the deluxe sidewinder so I can rewind the size L bobbin thread onto Class 15 bobbins. At one time I used only cotton threads, top and bottom . Now that the myths about using polyester have been debunked, I now use whatever thread works well with whatever project I am doing. No hard and fast rules here.