Apple used its autumn hardware event to do something it hasn't done in years — introduce an entirely new iPhone form factor. The iPhone Duo, the company's first foldable phone, opens book-style into a 7.6-inch inner display that Apple calls the largest screen ever built into an iPhone, while a 5.4-inch outer display handles everyday use when the phone is closed. Design and Build Built from grade-5 titanium with a mirror-polished finish, the Duo is offered in two colorways — s