Stainless steel duplex stainless steels are achieved with an overall lower alloy content than similar-performing super-austenitic grades, making their use cost-effective for many applications. Duplex grades are characterized into groups based on their alloy content and corrosion resistance. Precipitation hardening stainless steels have corrosion resistance comparable to austenitic varieties, but can be precipitation hardened to even higher strengths than the other martensitic grades. The most common, 17-4PH, uses about 17% chromium and 4% nickel. The designation "CRES" is used in various industries to refer to corrosion-resistant steel. Most mentions of CRES refer to stainless steel, although the correspondence is not absolute, because
Stainless steel both the Petronas Twin Towers and the Jin Mao Building, two of the world's tallest skyscrapers. The Parliament House of Australia in Canberra has a stainless steel flagpole weighing over . The aeration building in the Edmonton Composting Facility, the size of 14 hockey rinks, is the largest stainless steel building in North America. La Geode in Paris is a nearly spherical building. The dome is composed of 6433 polished stainless steel equilateral triangles that form the sphere that reflects the sky. Stainless steel is quite frequently used for pedestrian and for road bridges. Product forms are tubes (Helix bridge),