Drop forged and heat treated to ANSI specificationsChrome Vanadium SteelPrecisely machined open end and box end to exact specificationsComes with a PVC storage case and organizerSizes: 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4", 13/16", 7/8"