US Standard Length. Water hardened carbon tool steel, SK3 (content ratio of carbon, 1-1.1%), for taps, dies, chisels, etc. SK5 type (content ratio of carbon, 0.8- 0.9%) tool steel is for stamping plates for letters and figures or as saw blades. Annealed and processed for the easiest machinability. If you require a length other than the standard mentioned, please specify when ordering.