It&#x27;s basically what they said in during the presentation: it&#x27;s a 7000 alloy as used in aerospace industries[0], and it&#x27;s a new alloy (proprietary, not a standard spec). The apple watch also uses a proprietary 7000 alloy (whether it&#x27;s the same alloy is unknown at this point)<p>[0] not solely, they&#x27;re also used in bike frames. Basically 7000 is zinc alloys, and have the highest available tensile strength, rivalling low-level steels at a third the density.