TenaBrix® Polypropylene Synthetic Macrofiber is high quality polypropylene in large structure of fibers, produced by special molding process and surface modification to increase toughness of concrete. TenaBrix® Polypropylene Synthetic macrofibers can be thought of like steel fibers for concrete reinforcement applications. The physical characteristics of these fibers (length, tensile strength, diameter, etc.) are all different, when compared to traditional synthetic micros.