Polypropylene or olefin fibers are petroleum-based products that are derived from propylene and ethylene gases. These fibers are strong, quick drying, abrasion resistant, as well as mildew, soil, and stain resistant. In fact, they are the most stain-resistant synthetic fiber on the market today. Olefin, which has a soft wool-like feel, is one of the more widely used synthetic fibers for machine made rugs. Polypropylene can be heat-set to give it more durability and less luster, for a look that is also similar to wool. Polypropylene/olefin rugs are popular but because they are lightweight and affordable, however they may not be the best choice for areas with high traffic.