4" OD X 45 Degree Carbon Fiber - Matte FinishThis 4" OD carbon fiber elbow is used in air intake systems. Weighs 35 40% less than aluminum, yet is just as strong. Very attractive appearance. Our carbon fiber is 3K carbon fiber embedded in clear epoxy (wet process) and given a matte finish. Each of the bundles you see in the item consists of 3000 tiny fibers of pure carbon. The weave is twill, which means the bundles going one direction are spaced slightly wider than the bundles going the other