The iPhone Duo debuts on October 23 and starts at $1,999.

The iPhone Duo's inner display uses a complicated, multi-layer structure that Apple says will hold up to wear and tear. There are 10 ultrathin layers in total, including a nano-textured cover layer made from a custom polymer that Apple says is up to 40 percent stiffer than "other materials used in the industry," which presumably means other foldable devices.

Ahead of the launch of the foldable iPhone Duo, rumors suggested Apple was focused on eliminating the crease between the device's two displays. All foldables have a visible crease, and it often becomes easier to see over time from constant folding and unfolding. On the iPhone Duo product page, one of Apple's FAQs concerns the crease. "Does the inner display of iPhone Duo show a crease where it folds?" reads the question.

The competition is “absolutely welcome” by the pioneering Korean giant, but Samsung warns that the device’s “weight” is crucial.

The iPhone with a folding screen is the first radical redesign of Apple’s flagship handset in years. The iPhone Duo will cost $1,999 when it arrives in October.