BS A 318:1997 Nuts, hexagonal, slotted (castellated), reduced height, reduced across flats, with MJ threads, classifications. 450 MPa (at ambient temperature)/425 degreesC, 600 MPa (at ambient temperature)/235 degreesC, 600 MPa (at ambient temperature)/315 degreesC, 600 MPa (at ambient temperature)/650 degreesC,

standard by BSI Group, 11/15/1997