Markforged 150cc Kevlar CFF SpoolMarkforged 150cc Kevlar CFF spool Kevlar possesses excellent durability, making it optimal for parts that experience repeated and sudden loading. Parts with inlaid continuous kevlar fiber are setting benchmarks in the market and, through a patent, only possible on Markforged systems. As stiff as fiberglass and much more ductile, it can be used for a wide variety of applications.