Form: This specification covers one type of continuous multifilament carbon fibers in the form of a tow or yarn (when twisted). The weight per unit length of the tow or yarn is governed by the filament count which is identified by the supplier's grade or material designation. Classification: Carbon tow or yarn@ derived from a polyacrylonitrile precursor@ with typical 400 ksi (2758 MPa) tensile strength and 40 Msi (276 GPa) tensile modulus for use in general purpose structural composites requiring high tensile strength and moderately high modulus of elasticity in tension.