be in the fabric and vice versa suitable ranges for this feed tension includes from about 2 to 4 cn for 22 dtex spandex and from about 4 to 6 cn for 44 dtex spandex in commercial circular knitting machines with these feed tension settings and the additional tensions imposed by subsequent yarn path friction the spandex in commercial knitting machines normally will be drafted significantly more than 2 5 u00d7 minimizing the spandex friction between the supply package and the knit stitch helps keep the spandex feed tensions sufficiently high for reliable spandex feeding when the spandex draft in about 2 5 u00d7 or less the structural design of a circular knit fabric can be characterized in part by the u201c openness u201d of each knit stitch this u201c openness u201d may be related to the percentage of the area that is open versus that which is covered by the yarn in each stitch see e g fig1 and 3 and is thus related to fabric basis weight and elongation potential for rigid non elastic weft knit fabrics the cover factor u201c cf u201d is well known as a relative measure of openness the cover factor is a ratio and is defined as where tex is the grams weight of 1000 meters of the 2gt polyester yarn and is also equal to 10 dtex and l is the stitch length in millimeters fig3 is a schematic of a single knit jersey stitch pattern one of the stitches in the pattern has been highlighted to show how the stitch length u201c l u201d is defined the knitting method can produce commercially useful circular knit elastic single jersey fabrics plated from bare spandex and 2gt polyester yarn without heat setting with spandex draft at about 2.