Isacord 40wt polyester embroidery thread is simply the best! At nearly twice the strength and without the shrink of rayon thread, Isacord is the smoothest running and most reliable thread produced for machine embroidery and decorative stitching. It has been engineered to provide just the right amount of elasticity to allow for high speed running without looping or puckering while virtually eliminating thread breaks. Exact shades are continually produced from batch to batch so there are no worries about running out and having the new spool not match. It is also colorfast against light, boiling, washing, rubbing and bleach!