52100 Made up of Carbon: .90 1.05%, Chromium: 1.30 1.60%, Manganese: .95 1.25%, Nickel: .30%, Phosphorus: .025 - .030%, Sulfur: .025%, Silicon: .15 - .30%, Copper: .20 - .30%, Aluminum: .050% This steel is primarily used in the making of ball bearings, but has recently been made available in bar stock and is an excellent steel for use in kitchen knives. It has better edge retention than its cousin 5160, but is not as tough. We have a number of makers that use this steel in kitchen knives including; Devin Thomas, Stephan Fowler, Bob Kramer (through Henckels) Mark Richmond's Ultimatum. It is very reactive so wiping down and drying should be done after every use. The steel is easy to sharpen.