I have a Sidewinder bobbin winder that I stole from my mother
. My Bernina uses the giant bobbins (which I love), but I don't have a lot of them. If I have left over thread that I am not going to use soon, such as green, purple or yellow, I will use the Sidewinder to move that thread to a smaller plastic or metal bobbin from an older machine. Then, when needed, I can wind the thread from the small bobbin back onto a Bernina bobbin. Now infrequently used thread is not taking up valuable bobbin space.