This European standard specifies the characteristics of hexagon plain nuts@ reduced height@ reduced across flats@ in heat resisting steel@ silver plated@ for aerospace applications. Classification: 600 MPa1)/425 ??). 1) Corresponds to the minimum tensile stress which the nut is able to withstand at ambient temperature without breaking or cracking when tested with a bolt of a higher strength class. 2) Maximum temperature that the nut is able to withstand@ without permanent alteration to its original characteristics@ after ambient temperature has been restored. The maximum temperature is conditioned by the material.