Type: This procurement specification covers aircraft quality metric spanner nuts for retaining shaft mounted parts. Nuts are made from a corrosion and heat resistant age hardenable iron base alloy of the type identified under the Unified Numbering System at UNS S66286@ and silver plated. Thread shear proof strength at room temperature is 450 MPa. Application: Primarily for aerospace propulsion system applications to retain parts on shafts where a good resistance to relaxation is required.