Apple explains the iPhone Duo's inner display uses a complicated, multi-layer structure designed for durability. There are 10 ultrathin layers in total, including a nano-textured cover layer made from a custom polymer that is up to 40 percent stiffer than other materials used in the industry. Apple added high-strength glass above and below the folding display panel, along with a titanium plate at the bottom of the stack.

Custom adhesives allow the layers to glide past one another like the pages of a book, relieving bend stress. The exterior nano-texture layer reduces glare and minimizes crease visibility, with a scratch-resistant coating on top. The outer display is protected by Ceramic Shield 2, while the back uses Ceramic Shield.

The inner display uses the custom polymer cover instead of Ceramic Shield. Both displays support ProMotion, Always-On, and True Tone, offering 3,000 nits of peak outdoor brightness.