Light weight superfine Drumohr 140S wool crewneck for smart-elegant single wear on top of cotton or wool slacks with white sneakers. An S number on the label of wool suits or other tailored apparel, wool fabric, or yarn, indicates the fineness of the wool fiber used in the making of the apparel, as measured by its maximum diameter in micrometres. Fiber fineness is one of the factors determining the quality and performance of a wool product.