Simplicity SideWinder Portable Bobbin Winder Transfer thread from spool to bobbin effortlessly and quickly; adjustable tension knob to accommodate different thicknesses of thread Portable, and runs on two aa batteries or a power cord so it can be taken to classes Automatic shut-off when bobbin is full. Voltage: 120 Volts Convenient and compact for home and bringing to class Includes machine, AC power cord/adapter Convenient and compact for home and bringing to class Includes machine, AC power cord/adapter Easily fill bobbins without having to thread and unthread Accommodates all bobbins except viking