The S number of fiber, and hence of yarn, fabric, or garments made of that fiber, is determined using the international standard promulgated by the International Wool Textile Organisation (IWTO). The International Wool Textile Organisation (IWTO) is the promulgator of the "Fabric Labelling Code of Practice" which governs the use of the "S" and "Super S" designations for fine wool and wool blend fabrics. The Code defines the S number by correlation to maximum fiber diameter. For example, 80s must have maximum fiber diameter of 19.75 micrometres or finer and 90s, 19.25 micrometres or finer. This scale continues to the 210s at 13.25 micrometre or finer. Thus each step of ten (as from 80s to 90s or 90s to 100s) corresponds to 0.5 micrometre less in allowed maximum fiber diameter. It has been proposed to extend the scale to 250s at 11.25 micrometre or finer. IWTO is the international body representing the interests of the world's wool textile trade and industry. IWTO membership covers wool growers, traders, primary processors, spinners, weavers, garment makers and retailers of wool and allied fibers in its member-countries, as well as all kinds of organizations related to wool products and the wool business in general. In the United States labeling of wool products is regulated by the "Wool Products Labeling Act of 1939" (15 U.S.C. § 68). The Act was modified, for wool products manufactured on or after January 1, 2007, by the "Wool Suit Fabric Labeling Fairness and International Standards Conforming Act" which defined the use of the Super S and S designations in a manner conforming to the IWTO Code. The U.S. defines the S numbers for 80s to 250s. Violation of the WPLA may carry a substantial penalty.