BS A 316:1997 Nuts, hexagonal, slotted (castellated), normal height, normal across flats, with MJ threads, classifications. 600 MPa (at ambient temperature)/120 degreesC, 600 MPa (at ambient temperature)/235 degreesC, 900 MPa (at ambient temperature)/425 degreesC, 1100 MPa (at ambient temperature)/235 degreesC, 1

standard by BSI Group, 11/15/1997