Each flip socket size meets a minimum of 1.3 times the ANSI/ASME standard for proof torque, The flip sockets are made from 4140 Chromium-Molybdenum steel, The 3-inch extension is made from 6140 Chromium-Vanadium steel, All pieces have a corrosion-resistant manganese phosphate coating, The included 3-inch extension works for both types of anvils found on 1/2 inch drive impact wrenches.