Twisted into a spiral and attached to a woven or knit synthetic tape. A chain consists of individual teeth, usually metal, attached to a cotton or cotton-blend tape. A coil, being lightweight and flexible, is ideal for light- to medium-weight fabrics. Although chains come in lightweight form too, they are slightly more rigid, which can cause buckling on a lightweight fabric, and thus are best used on medium to heavy fabrics. Zipper length is specified on the pattern envelope. Buy this length unless experience has shown the recommended lengths