Markforged 150cc Carbon Fiber SpoolMarkforged Carbon Fiber 150cc spool Carbon Fiber has the highest strength to weight ratio of our reinforcing fibers. Parts with inlaid continuous carbon fiber are setting benchmarks in the market and, through a patent, only possible on Markforged systems. Six times stronger and eighteen times stiffer than Onyx, Carbon Fiber reinforcement is commonly used for parts that replace machined aluminum.