I think they are a waste of money. Every machine will wind a bobbin. I wind five at a time. While winding I can clean my bobbin case, oil the machine, clean up the area around my machine or call a friend. I would rather spend the $25 to 30 on FABRIC! To never run out of wound bobbins; when a sewing session is done just wind any empy bobbins you have before turning off your machine. I have a set in light gray and dark gray. I do all my pieceing and sewing with these two colors. I used to by matching thread for everything I did......was that crazy or what.
Connie