This specification defines the requirements for 500 and 700 MPa minimum tensile strength austenitic corrosion resistant steel externally threaded metric fasteners procured under part numbers listed on part standards which refer to this specification. Drawings may carry notes which modify the requirements of this specification. Receiving contractors may reject any lot which does not conform. The specification includes mechanical property requirements for the following four classes of fasteners: Type 1 - Hex Head Type 2 - Pan Head Type 3 - Socket Head Type 4 - 100??lush Head Recommendations for improvements or corrections of this specification should be directed to the NASC representative of a using aerospace company or to the National Aerospace Standards Committee@ Aerospace Industries Association@ 1250 Eye Street N. W.@ Washington@ D.C. 20005.