The A5 Castle Nut in Black is an essential component for securing buffer tubes in A5 buffer system configurations.A5 Castle Nut - Black FinishCompatible with A5 buffer tube systemsDurable black finish for corrosion resistancePrecision threading for secure installationSKU: CN5FThis castle nut provides reliable retention and proper torque specifications for A5 buffer tube assemblies in rifle builds and maintenance applications.