Tool Steel Rectangular Bar, Material Tool Steel, Material Grade O1, Thickness 0.25 in, Thickness Tolerance +/-0.001 in, Overall Length 18 in, Overall Width 4 in, Fabrication Hot Rolled, Heat Treatable Heat Treatable, Heat Treatment Oil-Hardened, Mechanical Finish Precision Ground, Yield Strength 55,000 psi, Tensile Strength 95,000 psi, Brinell Hardness 177 BHN, Rockwell Hardness 18 HRC, Standards AISI O-1, ASTM A681-08, FEDERAL QQT 570 REV C, SAE J437, UNS T31501