For use with rayon and other specialty machine embroidery threads including polyesters. The special scarf, long smooth groove, and large eye, of this needle protect these more fragile threads and guard against excess friction. The shank(top part) of these needles have one flat side and one rounded side. These will fit all "household" models of Brother, Janome, Singer, Pfaff, Bernina, Viking, Elna, Kenmore, Baby Lock, Simplicity, Necchi, White and many others.