This tag represents aluminum alloyed with zinc, which – along with a smaller percentage of magnesium – is material in producing one of the strongest heat-treated aluminum alloys. Apart from the abovementioned elements, this alloy also usually contains iron, silicon, manganese, chromium, copper, and traces of other elements. Class 7000 alloys are often referred to as “aviation duralumin” due to their frequent use in airplane construction and other high-strain parts. Some of their better-known qualities include increased strength and lower resistance to corrosion, which means the alloy ages naturally and does not require heat treatment following frame welding. The 7005 aluminum alloy reaches a tensile strength of 400 MPa and density of 2.78 g/cm3.