Foldables are the hardest phones to case correctly, because a case for a flip phone is really two cases joined by nothing. Each half has to grip its own panel firmly enough to stay on, without adding thickness at the hinge, without stopping the phone closing flat, and without covering the cover display. The Galaxy Z Flip 3 and Z Flip 4 look nearly identical closed, and their cases are still not interchangeable.
The dimensions, folded and unfolded
- Galaxy Z Flip 3 (SM-F711): unfolded 166.0 x 72.2 x 6.9 mm; folded 86.4 x 72.2 x 15.9–17.1 mm; 183 g; 6.7-inch main display, 1.9-inch cover display; 3,300 mAh
- Galaxy Z Flip 4 (SM-F721): unfolded 165.2 x 71.9 x 6.9 mm; folded 84.9 x 71.9 x 15.9–17.1 mm; 187 g; 6.7-inch main display, 1.9-inch cover display; 3,700 mAh
The Flip 4 is 0.8 mm shorter unfolded, 0.3 mm narrower, and — the important one — 1.5 mm shorter when folded. Samsung achieved that by redesigning the hinge to be narrower, which pulled the two halves closer together.
Why the hinge redesign breaks case compatibility
On a flip phone, the case halves sit right up against the hinge assembly. The Flip 4's hinge is physically slimmer, so a Flip 4 case has its inner edge cut closer to the fold line. Put a Flip 3 case on a Flip 4 and there is a visible gap at the hinge with the phone's frame exposed; put a Flip 4 case on a Flip 3 and the case edge fouls the hinge housing, which stops the phone closing completely flat.
A foldable that does not close flat is a foldable collecting grit in the fold, and grit in the fold is what damages the inner display. This is not a cosmetic issue.
The Flip 4's battery also grew from 3,300 to 3,700 mAh, and its charging jumped from 15 W to 25 W — which means more heat under the back panel. A case that traps that heat is worth avoiding on the Flip 4 specifically.
Choosing a Z Flip 4 case
Priorities in order: hinge clearance, cover-display clearance, camera protection, and something to grip. A ring stand solves the grip problem specifically — flip phones are slippery when folded and awkward to hold one-handed when open.
If you want the hinge itself covered rather than left open, a dedicated hinge-protection case wraps that section, which is the single most vulnerable part of the phone.
The Galaxy Z Flip 4 Cases collection covers wallet, kickstand, strap and rugged formats cut to the 84.9 mm folded body.
Choosing a Z Flip 3 case
The Flip 3 has the smaller battery of the two and is now several years into service, so heat management matters. It also has the taller folded profile, so its cases run slightly longer. A military-grade two-piece shell is the standard answer for anyone who actually uses the phone rather than babying it.
See the Galaxy Z Flip 3 Cases collection.
Screen protectors on a foldable: read this before you buy
The inner display of a Z Flip is not glass. It is a plastic-topped flexible panel with a factory-applied protective layer that Samsung fits in the plant. Do not put standard tempered glass on it — glass cannot fold, and attempting it will crease or crack the panel.
What you can protect:
- The cover display (1.9 inches on both models). This is regular Gorilla Glass Victus and takes tempered glass normally.
- The camera lenses, which sit alongside the cover display and are exposed whenever the phone is closed and in a pocket.
- The inner panel, only with a flexible film explicitly sold for foldables — and only if the factory layer has already been removed or damaged.
If the factory layer on your inner screen is peeling at the edges, that is normal wear and Samsung service centres can replace it. Peeling it off yourself and leaving the panel bare is how these screens get scratched.
Frequently asked questions
Will a Z Flip 5 case fit a Z Flip 4? No. The Flip 5 folds completely flat with no hinge gap and has a 3.4-inch cover display against the Flip 4's 1.9 inches. The cover-display cutout alone rules it out.
Do Flip 3 and Flip 4 have the same water rating? Both carry IPX8, which covers fresh-water immersion but includes no dust rating. Grit in the hinge is a genuine risk on both, which is another reason to keep the phone closing flat.
Can I use a magnetic car mount with a Z Flip? Only via a case with a metal plate or ring. Neither phone has built-in magnets, and a mount that grips the folded phone across the hinge will stress it.
Will a case stop the phone closing properly? A correctly cut one will not. If yours leaves a visible wedge at the top when closed, it is either the wrong model or a poor cut — either way, replace it before grit gets in.
How do I check which Flip I have? Settings > About phone > Model number — SM-F711 is the Flip 3, SM-F721 is the Flip 4. For fit questions, use the Contact page or 978-797-0223.
The bottom line
1.5 mm off the folded height and a slimmer hinge mean Flip 3 and Flip 4 cases do not swap. On a foldable that is not a cosmetic problem — a case that stops the phone closing flat lets grit into the fold, which is the most expensive failure these phones have.