Carbon Fiber FR is a flame-retardant variant of Markforged’s unique, ultra-high-strength Continuous Carbon Fiber — when used to reinforce a Composite Base material like Onyx FR, it can yield parts as strong as 6061-T6 Aluminum. It’s extremely stiff and strong, and can be precisely laid down in a wide variety of geometries. Programmatically trace curved features, reinforce holes, and mimic unidirectional fiber layups — all within a few clicks.