Sulky 30 weight is 1/3 heavier than 40 wt. and is ideal for top-stitching, quilting, satin stitch decorative stitches (fills them in completely) and it is an exceptionally strong, silky rayon thread. When enlarging computerized designs, 30 wt, will fill them in more completely than 40 wt. It is colorfast, both washable and dry cleanable. It is recommended that no bleach or whitening agents be used when laundering. King Size has 500 yards on the spool. Spool size has 180 yards.