The length of fibers is one of the most important factors determining its quality because natural and long fibers get stronger and more resilient. The length of cotton fibers is usually between 20-40 mm and itself has short and medium-sized varieties. The length of the wool fibers to make rug threads is typically more than (5) centimeters, and the fibers with less length should not account for more than 5 percent of the total weight of the wool.