Sidewinder Portable Bobbin Winder fills bobbins with the push of a button. The compact design is easy to carry to class. There's no need to unthread and re-thread your sewing machine to wind more bobbins. Runs with a power cord that is included or on 2 AA batteries. It accommodates all bobbins that have a standard round center hole. Does NOT accommodate Singer Centaur II, Viking & Futura sewing machines bobbins.