Core material for clothes making In order to maintain strength in areas that are prone to load on the fabric, the straight part of the fabric is not too stretchy. Flat... Straight parts such as the shoulder lines, where load is subject to the weight of the fabric; Bias... Mainly curved parts such as neck and armholes; Half bias... Mainly gentle curves such as the waistline and hip line; Size: 0.35 inches (9 mm) x 9.8 feet (25 m) ■Material: 65% polyester, 35% cotton.