iPhone Duo Specs, Price & Dimensions (Confirmed)

Everyone is writing about the 5.2 mm. We design foldable cases, so we went looking at the other number.

By Priya Nair · FoldifyCase foldable case design team · 10 September 2026

The headline, and the number underneath it

Apple's line is that the iPhone Duo is the thinnest iPhone ever made — 5.2 mm. That is true, and it is a genuine engineering achievement. Unfolded, it is thinner than the iPhone Air.

It is also, closed, the thickest folding phone in its class.

A foldable spends most of its life closed, in a pocket. The number you actually live with is 11.3 mm — 2.4 mm more than the Z Fold 8 Ultra, which is a lot when you are talking about something you sit down with.

And here is the part that is our problem rather than Apple's: a case only ever adds to the closed number. A two-piece foldable case puts material on both outer faces. At a 1 mm wall per half — which is slim, not rugged — you are looking at roughly 13.3 mm in the pocket. Rugged designs will push past 15 mm.

Then there is the weight

254 g. That is the figure that made us sit up.

Titanium is strong, but it is not light. Grade 5 titanium in both the frame and the hinge is what gives the Duo its rigidity — and 53 g more than the Z Fold 8.

Add a case and you are carrying something close to 300 g. That is a real consideration, and it shapes what we would build: on this device, every gram of case has to justify itself. Chunky rugged designs that work fine on a 200 g phone become genuinely unpleasant here.

The full confirmed spec sheet

The spec nobody is leading with, and probably should be

If you have followed foldables for any length of time, you will know why this matters. Dust in the hinge has been the defining failure mode of the category. Grit works its way into the mechanism, then into the fold of the inner panel, and the damage is expensive and usually terminal. Samsung has been chipping away at it for years and has not closed the gap.

Apple appears to have closed it on the first try. If that rating holds up in real-world use — and we will be watching teardowns closely — it is the most significant thing about this device, and it barely got a mention on stage.

It also changes what a case is for. On a Samsung foldable, part of the case's job is keeping grit out of the hinge zone. On a genuinely dust-tight device, that pressure comes off, and the case can concentrate on what it is actually good at: drop energy, corner protection, and grip on a heavy object.

What Apple left out

Two absences worth naming at US$1,999.

No telephoto lens. Two 48MP cameras — wide and ultrawide. The Galaxy Z Fold 8 Ultra has a 200MP main, a 50MP ultrawide and a 10MP 3× telephoto for US$2,099. If you photograph anything at distance, that is a real gap.

No Face ID. Touch ID lives in the side button instead. We wrote about why that rules out an entire category of case design before the announcement, and the confirmation makes it concrete: any case that covers the power button will break the unlock. Capacitive sensors need bare skin. If you are shopping rugged, check for an open, chamfered cutout at that button before anything else.

Will any existing case fit? No — and here is exactly why

The iPhone Duo's folded footprint is, interestingly, closest to Samsung's wide Galaxy Z Fold 8 rather than the tall Ultra.

Against the Z Fold 8 it is 6.1 mm shorter, 2.2 mm wider and 1.6 mm thicker. In a photograph those two devices look like siblings. In a case mould they are unrelated.

To put that in perspective: a camera cutout machined 0.3 mm off centre will vignette an ultrawide shot. We are talking about differences five to twenty times that size, in all three axes at once. There is no adaptation, no stretch, no "close enough". The Duo needs tooling cut for the Duo.

What we would design for this device

Reading the spec sheet as a brief, four things stand out.

1. Thin walls, aggressive corners. At 11.3 mm and 254 g, bulk is the enemy. Put the material where drops actually land — corners and the hinge edge — and take it off everywhere else.
2. An open, chamfered power-button cutout. Non-negotiable with side-button Touch ID.
3. Nothing touching the inner panel. The Nano Texture finish is a coated surface, and coated surfaces mark. Raised bezels, zero contact when closed.
4. Magnet transparency, not magnet addition. The Duo has 25W MagSafe built in. Unlike our Samsung cases, which add a magnet array, a Duo case has to get out of the way of one and keep it aligned.

One bonus: eSIM only means no SIM tray, which is one less cutout to get wrong and slightly more structural continuity along the bottom rail. Small mercy, genuinely useful.

When you can actually buy a case

Pre-orders open 16 October and the device ships 23 October. Cases that genuinely fit come after that, not before — because tooling requires a retail unit on a bench with calipers on it.

You will see iPhone Duo cases listed within days. They will be moulded from the same leaked CAD that had this device down as the "iPhone Fold" with different dimensions entirely. We set out the full reasoning in why you will wait weeks for a case that actually fits, and nothing about the announcement changes it.

So — is it any good?

We design cases, not phone reviews, so take this as a structural read rather than a verdict.

Apple has done the hard part properly. IP68 on a book-style foldable is a first, and it addresses the failure mode that has quietly killed more foldables than drops ever have. The titanium hinge, the Ceramic Shield 2 cover glass and the claimed small crease all point the same way: this is built to survive being a foldable, which is not something we could say about the first generation from anyone else.

What Apple traded for it is weight and closed thickness. 254 g and 11.3 mm is the cost of that titanium and that ingress sealing. Whether that trade is right for you depends entirely on whether you have ever had grit in a hinge.

And at US$1,999 with no telephoto, the camera system is the weakest part of the sheet. The Z Fold 8 Ultra costs US$100 more and gives you a 200MP main and a 3× telephoto.

Frequently asked questions

What is the iPhone Duo called and when does it launch?

Apple's first foldable is the iPhone Duo, announced 9 September 2026. Pre-orders open 16 October 2026 and it ships 23 October 2026.

How much does the iPhone Duo cost?

From US$1,999 for 256GB, rising to US$3,199 for 2TB. European pricing is around €2,300. Check Apple's regional store pages for local pricing.

What are the iPhone Duo's dimensions?

Folded it is 117.8 × 84.1 × 11.3 mm. Unfolded it is 117.8 × 164.6 × 5.2 mm. It weighs 254 g. At 5.2 mm unfolded it is Apple's thinnest iPhone; at 11.3 mm folded it is thicker than any current Samsung book-style foldable.

Is the iPhone Duo waterproof?

It carries an IP68 rating — fully dust tight and immersible to 6 metres for 30 minutes. That is notably better than the IP48 rating on Samsung's Galaxy Z Fold 8 and Z Fold 8 Ultra, which resist objects larger than 1 mm but are not dust tight.

Does the iPhone Duo have Face ID?

No. It uses Touch ID built into the side button. This means a case must leave that button open — a covered power button will prevent the fingerprint sensor from reading.

Will a Galaxy Z Fold case fit the iPhone Duo?

No. The Duo folds to 117.8 × 84.1 × 11.3 mm, the Galaxy Z Fold 8 to 123.9 × 81.9 × 9.7 mm and the Z Fold 8 Ultra to 158.4 × 72.8 × 8.9 mm. All three differ in every axis, and camera and button positions differ too. Each needs its own tooling.

Does the iPhone Duo support a stylus?

Yes, stylus support is listed in the specifications. Apple has not detailed which stylus or whether one is included.

When will iPhone Duo cases be available?

Cases that genuinely fit require measurements taken from a shipping device, so expect them after the 23 October release rather than before. Cases listed before then are moulded from leaked estimates.

Related guides

• Touch ID and what it rules out for case design
• Why you will wait weeks for a case that actually fits
• iPhone foldable cases: what to look for
• What to budget for a foldable iPhone
• Galaxy Z Fold 8 and Z Fold 8 Ultra: confirmed specs

Sources

• GSMArena — Apple iPhone Duo full specifications
• Engadget — Apple announces the iPhone Duo
• TechCrunch — Apple unveils its first foldable, the iPhone Duo
• MacRumors — iPhone Duo beats iPhone Air as Apple's thinnest iPhone, but only when open
• GSMArena — Galaxy Z Fold8 Ultra specifications
• GSMArena — Galaxy Z Fold8 specifications