Abstract: The mechanical stress indicator includes two stress indicating rings disposed between engagable fasteners. The stress indicating rings can assume three distinct cooperative positions, corresponding to a less than optimally tight condition of the fastener, an optimum tightness condition and an overtight condition. When the fastener arrangement is in the less than optimally tight condition the mos visually predominant surfaces are of a first code, which can be a first color. When the fastener arrangement is tightened to an optimum tightness condition the stress indicator is deflected and the most visually predominant surfaces, which differ from those of the less than optimally tight condition, are of a second code, which can be a second color that corresponds with the optimum torque condition.