Blue Temper Spring Steel – 0.015 Inch Thick x 3.00″ Width x 600 Inch (50 ft) Length Thickness Tolerance ±0.001″ Width tolerance is ±0.010″. Length tolerance is ±1/2″. C1095 Blue Tempered and Polished Spring Steel. Rockwell hardness C 50. MIL-S-7947, AISI-1095, SAE- 1095, and AMS-5122.