This combination wrench is used to adjust the speed reduction pulley and bracket on the Ultrafeed^® and Leatherwork^® Sewing Machines. One end fits the 12mm bolt to adjust the up and down position of the bracket to the balance wheel. The other end is for the 5mm square bolt for adjusting the tension on both belts. The steel wrench is black oxide treated, which adds corrosion resistance and minimized light reflection. The tool's size provides a firm grip and allows you to reach the bolts without difficulty.