Tool Steel Flat Stock, Steel Material, Width 3 in, Thickness 5/16 in, Fractional Size 5/16 in x 3 in x 18 in, Finish Unfinished, Length 18 in, Length Tolerance +0.125 to +0.250 in, Hardness Scale 220 to 255 BHN; Rockwell B97 to 102, Grade D2, Standards ASTM-A681, FED-QQ-T-570, SAE-J-437