This standard specifies the characteristics of heat resisting steel, facing/packing washers for use in non load spreading aerospace applications at temperatures not exceeding 650 °C. They are intended primarily for use as facing/packing washers under the head of bolts with strength classification up to 1 250 MPa to provide adequate clamping of slotted or recessed surfaces (especially on brackets and pipe clippings) and used for adjusting grip lengths of bolts.