I also use prewounds. I asked my sewing machine repairman if they could be used in my machine (Babylock Quest+), and he gave me one to try. It was wonderful!!! They last forever, and help achieve a very accurate 1/4 inch seam because there is less bulk. I purchased 100 bobbins for $32!!! I've been using them for piecing and quilting, including FMQ, with no problems! By the way, mine have NO sides, cardboard or plastic.