Sulky Premier Invisible thread is a very fine .004 monofilament that is soft enough for baby quilts or garments that will be worn next to the skin. Quilters prefer Sulky Polyester Invisible thread over nylon because it has a more flexible, soft touch. It is much more heat tolerant than nylon; it will not melt with normal ironing through the cotton setting. It also works well in the bobbin and is ideal for sergers. Sulky Invisible Thread does not fuzz, fray or shrink. Choose smoke for darker fabrics and clear for lighter fabrics.