1.1 This specification covers five grades of bolting with twelve classes of yield strength ranging from 50 to 120 ksi [345 to 827 MPa] for use in high-temperature service such as fasteners for pressure vessel and valve flanges. See Specification for the definition of bolting. The material requires special processing and is not intended for general purpose applications. 1.2 The following referenced general requirements are indispensable for application of this specification: Specification . 1.3 Supplementary Requirements are provided for use at the option of the purchaser. The Supplementary Requirements shall only apply when specified individually by the purchaser in the purchase order or contract. 1.4 This specification is expressed in both inch-pound units and in SI units; however, unless the purchase order or contract specifies the applicable " M " specification designation (SI units), the inch-pound units shall apply. 1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.