SEW EASY! These slick space age washers eliminate the backlash in the bobbin when changing directions at high speed. Backlash creates "birds nests"in free-motion quilting and embroidery. Just drop a LITTLE GENIE in the bobbin case, replace bobbin and you're good to go! Fits all domestic machines. Designed by author, teacher and award winning quilter Sharon Schamber. Package of 12. Tough and long-lasting.