Prym Shirring Elastic Sewing Thread in Natural White. This highly elastic thread is 0.5mm thick and can be used as a shirring elastic on your sewing machine bobbin (shirring is two or more rows of elasticated gathers that are used to decorate parts of garments such as sleeves or the bodice of a shirt or dress). This elastic sewing thread can also be used as a knit-in thread when knitting and crocheting elastic hats and cuffs.