LaPierre Mega Magic Bobbin Washers ~ Mega Magic Bobbin Genies ~Size M Bobbin ... Special size for all long-arm machines using size "M" bobbin cases. Eliminates backlash & bird's nests on the underside of your quilt! Easy to use! Just drop Bobbin Genie into the bobbin case. Replace bobbin and insert into the machine. Long lasting! Super slippery, touch and durable! Designed by: Sharon Schamber Use during free-motion quilting, thread painting or embroidery when changing directions at high speed.