4340 is a high-strength, low-alloy steel containing chromium, nickel, and molybdenum that provides excellent toughness, fatigue strength, and wear resistance. Hex bars made from this heat-treatable 4340 alloy steel are commonly used for applications requiring high mechanical properties and durability, such as machine tools, automotive components, shafts, structural parts, and aerospace components. The hexagonal cross-section shape of the bar is well-suited for applications needing high strength and resistance to wear.