All polyesters and other manufactured fibers are not alike. The composition of each fiber is distinct and has its own set of physical characteristics. The United States Federal Trade Commission has defined and generically named man-made fibers, for instance, polyester, nylon, rayon, and spandex. Yet, each fiber in a category may be different as producers chemically and physically modify the basic composition of the generic fiber. Variations produced may provide benefits such as softer feel, brighter color, or greater warmth retention.