Square Montecarlo sunglasses with carbon frames and embossed "k" logo on the tips. Orange mirror polarized lenses. Carbon fiber is a material made up of fibers 5-10 microns in diameter, composed mainly of carbon atoms. The carbon atoms are bonded together in crystals that are roughly aligned parallel to the long axis of the fiber. The crystal alignment gives the fiber high strength based on volume. Several thousand carbon fibers are braided to form a yarn, which can be used by itself or woven into a fabric. Its high flexibility, resistance, low weight, tolerance to high temperatures, and low thermal expansion make carbon fiber the perfect material for sports.