This nut secures a threaded connection on the host harvester where a Class 8.8 fastener is specified. It is used on assemblies that experience high clamping loads, such as the attachment points for the header or the drive-train components on the machine. A nut that does not meet the hardness rating may loosen under vibration, leading to joint failure. Using a fastener with the correct hardness class ensures the clamp load matches the original design intent. On reinstallation, clean the threads and tighten to the torque value specified for the mating bolt.