Best Buy For Your Buck: Get 3 TIMES the thread for HALF the cost of a 250 yd. spool! Industry experts calculate that one 850 yd. spool of 40 Wt. Rayon thread can create 156,000 stitches. Sulky 40 Wt. Rayon embroidery thread has the same luster and soft, warm, natural look as silk with silkÂs smoothness, but it is stronger and less expensive. The vast majority of embroidery designs are digitized for Sulky 40 Wt. Rayon thread. Because of its excellent runability, unparalleled quality and huge selection of colors, Sulky is, and always has been, the first choice of machine embroiderers. Only Sulky Rayon threads are made exclusively from ENKA fibers, proven to be the highest quality rayon/viscose fibers in the world.