Hardened and tempered for longer life. High-quality chrome vanadium steel. Packaged in reusable plastic holder. Includes sizes: .05″, 1/16″, 5/64″, 3/32″, 7/64″, 1/8″, 9/64″, 5/32″, 3/16″, 7/32″, 1/4″, 5/16″, and 3/8″.