Twin Stretch needle size 4.0mm/75. Twin needles are used for practical sewing and decorative sewing such as pintucks, seam finishes and topstitching etc. The size of the needle is measured in "mm" from tip to tip (example 2mm needle has a 2mm space between the points). Stretch needles are designed for two way stretch knits, lycra, power net, silk jersey, spandex and highly elasticised synthetic fabrics, also ideal for sewing elastic. They have a specially designed scarf which prevents skipped stitches.