Foldable versus slab. Duo opens to a 7.6-inch inner panel and closes to a 5.4-inch outer (~90% of 18 Pro screen area when closed, per Apple). Pro Max is the large slab at $1299 start; Duo starts at $1999 / 256GB. Both list A20 Pro and a vapor chamber. We did not fold, drop, or battery-test either device.
| Spec | iPhone Duo | iPhone 18 Pro Max |
|---|---|---|
| Form | Foldable (first foldable iPhone, Apple) | Slab Pro Max |
| Display | Inner 7.6-inch; outer 5.4-inch (~90% of 18 Pro screen area when closed, Apple claim) | unknown (size not in sources we cite) |
| Chip | A20 Pro | A20 Pro |
| Thermal | Vapor chamber (Apple) | Vapor chamber (Apple) |
| Battery | Dual-battery (mAh unknown) | Apple claims the largest battery-life increase ever on iPhone (marketing claim — not measured here) |
| Camera | unknown | 48MP Fusion Main with variable aperture; smaller Dynamic Island (Apple) |
| Storage | Starts at 256GB | unknown starting capacity in sources we cite |
| RAM | unknown | unknown |
| Weight | unknown | unknown |
| Charging | unknown | unknown |
| Starting price | Starts $1999 (256GB) | $1299 (Apple)Lower start |
| Finishes | Two colors (names unknown) | Black, silver, glacier, burgundy |
| Availability | Pre-order Oct 16; availability Oct 23 | Pre-order Sat Sep 12; available Sep 18 |
Form factor
Apple says Duo keeps the same aspect ratio on inner and outer displays, with a nano-texture inner option claimed. Dual-battery is listed; mAh is unknown. Pro Max battery capacity is also unknown on this page; only Apple’s “largest increase ever” marketing line is on the Pro Max sheet.
Timing
Pro Max: pre-order Sep 12, available Sep 18. Duo: pre-order Oct 16, availability Oct 23. If you need a phone in September, the slab ships first on this calendar.
Apple — iPhone Duo Amazon search (no ASIN)
Apple — iPhone 18 Pro Max Amazon search (no ASIN)
Sources
Apple Newsroom, 9 September 2026.