BS A 321:1997 Nuts, anchor, self-locking, floating, self-aligning, single lug, with MJ threads, classifications: 900 MPa (at ambient temperature)/235 degreesC, 900 MPa (at ambient temperature)/315 degreesC and 900 MPa (at ambient temperature)/425 degreesC. Dimensions

standard by BSI Group, 10/15/1997