1.1 This specification covers black or galvanized welded or seamless threaded steel couplings for use with steel pipe in NPS 1/8 to NPS 20 [DN 6 to DN 500] inclusive (). Couplings ordered under this specification are intended for the uses outlined in the pipe specifications referencing this specification. The dimensionless designator NPS (nominal pipe size) and DN [diameter nominal] has been substituted in this standard for such traditional terms as nominal diameter, size, and nominal size.

1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. 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.