If you order products through our platform, run an accessories store, or manage a service center, you might notice the symbols 4sF-s and 4sD-i when looking at cases for foldable smartphones. They appear in our range of cases from various manufacturers, including our own brand Forcell. They help to identify products that, due to their materials, workmanship, or construction, do not fit into any of the previously sold product groups.
The number of foldable phone models is growing, and with them, accessories specifically designed for their build. It’s therefore worth knowing what lies behind these designations and why you won’t find them with every case for a foldable smartphone.
Table of Contents
Why do we use the designations 4sF-s and 4sD-i?
Known product groups help you quickly identify the type of case you are looking for. However, among accessories for foldable smartphones, there are models that cannot be reliably assigned to any of these groups. They differ in the materials used, the method of manufacturing, or the structural solutions related to the foldable casing.
For such products, the groups 4sF-s and 4sD-i were created. Thanks to them, cases that do not have an equivalent in the current offer receive a clear place in the catalog.
This is not, however, a division solely by phone model. If a case for a foldable phone is identical in terms of workmanship, materials, and details to products from an existing group, it is assigned to that group.
How to read the symbol step by step?
Each symbol consists of the same four elements:
Therefore, we expand 4sF-s as For Series Fold/Flip – Samsung, and 4sD-i as For Series Duo – iPhone.
What does the symbol look like in the product name?
The group designation appears in the full product name, next to the device model, brand, case variant, and its features. Examples from our offer:
Group 4sD-i – Forcell F-Protect line for iPhone Duo:
Case for iPhone Duo Forcell F-Protect 4sD-i Clear 2.5 mm Premium Hinge compatible with MagSafe transparent 0INT
Case for iPhone Duo Forcell F-Protect 4sD-i Smoke Hybrid Premium compatible with MagSafe black 0INT
Case for iPhone Duo Forcell F-Protect 4sD-i Smoke Hybrid Kickstand Premium compatible with MagSafe black 0INT
Case for iPhone Duo Forcell F-Protect 4sD-i Clear 2.0 mm Premium transparent 0INT
The listed models will soon be available in our sales offer.
It’s worth preparing for the launch of the new category now — the new iPhone Duo, Apple’s first foldable phone, will go on sale on October 23, 2026, and pre-sales will start on October 16 at 2:00 PM.
Group 4sF-s – Samsung Z Fold 8 / Z Flip 8:
Case for Samsung Z Fold 8 Ultra 4sF-s Clear transparent
Case for Samsung Z Fold 8 Ultra 4sF-s Clear compatible with MagSafe transparent
Case for Samsung Z Flip 8 4sF-s Hard black
Case for Samsung Z Flip 8 4sF-s Acrylic compatible with MagSafe dark blue.
Let’s break down the first name into its elements:
The symbol helps to identify the group, but the full name and product card indicate the compatibility of the case with the phone.
4sF-s: group of cases for foldable Samsung Fold and Flip phones
4sF-s includes cases for foldable Samsung phones from the Fold and Flip lines, which cannot be assigned to existing product groups due to their materials, workmanship, or details. In the platform menu, you will find them in a separate group, which makes it easier to browse models designed with a foldable form factor in mind.
Fold and Flip differ in dimensions and folding method. Thus, a common group designation does not mean that a specific case fits both devices. When ordering, always check the exact phone model indicated in the product name.
4sD-i: group of cases for iPhone Duo
4sD-i operates on the same principle for iPhone Duo. Cases whose characteristics do not allow them to be classified into groups already present in the offer are placed here.
However, there are exceptions. Clear Case Mag Cover MID for iPhone Duo remains in the MID group, because in terms of workmanship and materials used, it corresponds to other models in this group. Therefore, when compiling the offer of accessories for iPhone Duo, it is worth checking both 4sD-i and the existing product groups. The mere designation of a case for a foldable phone does not determine the name of its group.
iPhone Duo – the first foldable iPhone. What does it mean for the GSM accessories market?
A product group is not a compatibility list
The symbol 4sF-s or 4sD-i indicates how the product has been organized in the offer. It does not mean that one case will fit all devices from a given series. This applies particularly to foldable smartphones, where case dimensions and hinge solutions may differ between models.
Therefore, before ordering, check the full phone name and the compatibility list on the product page. The group facilitates finding the case; the product page confirms its fit.
What does the labeling system offer B2B Partners?
- Clearer ordering. Cases with a distinctive design for foldable smartphones can be found in their designated group.
- Consistency with the existing offer. Products identical in terms of workmanship and materials to an existing group remain in that group.
- Easier assortment completion. When searching for a case for a foldable model, you know why it’s worth checking both the new group and the groups already available on the platform.
- More precise store descriptions. You can separately indicate the type of case and its features, as well as the phone model it fits.
How to explain the labeling to the buyer?
Frequently Asked Questions about 4sF-s and 4sD-i designations
What does “4” mean in the 4sF-s symbol?
It’s an abbreviation of the English word for, meaning “dla” (for), written as a numeral.
What does the lowercase letter “s” after the four mean?
Series, meaning a series of devices.
What do the letters F and D mean?
F refers to the Fold/Flip line, and D to iPhone Duo.
Do all cases for foldable phones have the 4sF-s or 4sD-i designation?
No. If a model matches an existing product group in terms of craftsmanship, materials, and details, it is assigned to that group.
Why is the Clear Case Mag Cover MID for iPhone Duo not in the 4sD-i group?
Because it can be assigned to the MID group, which it resembles in terms of craftsmanship and materials used.
Does a case from the 4sF-s group fit both Z Fold 8 and Z Flip 8?
No. The group includes products for both lines, but a specific case is tailored to the model indicated in its name and on the product page.
Do you run a GSM store or service center? Check out our knowledge base
In the category GSM Store, we regularly publish practical materials for sellers: we advise on how to build and present an offer, select assortment, prepare displays, utilize seasonal sales opportunities, and promote the store online. You will also find comparisons of new devices there, as well as tips on which accessories are worth introducing for sale.
