Apple's foldable iPhone Ultra will arrive this fall with dual displays and an unusual authentication approach. The premium device will use Touch ID instead of Face ID, a surprising choice for Apple's top-tier product. When unfolded, the Ultra will measure just 4.5-4.8mm, making it even thinner than the iPhone Air's 5.6mm.

The authentication switch stems from space constraints in Apple's thinnest iPhone yet. Face ID would require separate components for each display, doubling the internal real estate needed. Touch ID integrated into the power button eliminates this requirement, allowing more space for battery and other components.

Despite offering cutting-edge foldable technology, Apple's authentication choice represents a compromise between design and functionality. The Ultra's thinness comes at the cost of facial recognition, positioning it as a specialized device rather than a direct upgrade to existing models.