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What is an IoT SIM? M2M SIM formats, environmental classes and eSIM explained
An IoT SIM, also called an M2M SIM, is the subscriber identity module and subscription used by a machine rather than a phone. "IoT SIM" is a market term, not a standardized product class: the standards describe machine-type communication, removable card formats, M2M-specific packages and environmental classes. A buyer should therefore ask which format, which environmental class and which subscription features a specific card actually has.
What makes a SIM an "IoT" or "M2M" SIM
3GPP describes an MTC Device as user equipment equipped for machine-type communication that talks through a mobile network to MTC servers or other devices. It distinguishes machine-type communication from human-to-human service by data communications, lower cost and effort, potentially very large numbers of terminals and, to a large extent, little traffic per terminal.
The same specification defines MTC Features such as Low Mobility and Small Data Transmissions. They are identified in the subscription and can be activated individually, and the specification notes that not every optimization suits every application. In practice, an "IoT SIM" offer is a combination of a card or embedded module and a subscription; ask which features, countries and management functions the specific offer includes rather than assuming them from the name.
Card formats: from plug-in to MFF2
ETSI TS 102 221 defines four removable formats. The plug-in UICC (second form factor), mini-UICC (third) and 4FF (fourth) are the removable cards a device slot is built for; their dimensions are fixed by the standard, so the slot in your device determines which one to order.
ETSI TS 102 671 adds two machine-to-machine form factors. MFF1 is described as well adapted for socketing, while MFF2 is a package layout that offers the possibility of a large central heatsink. Choosing MFF1 or MFF2 is a hardware design decision made with the module or device maker, not something a connectivity buyer can change after production.
| Format | Defined in | Size or note | Buyer check |
|---|---|---|---|
| Plug-in UICC (2FF) | ETSI TS 102 221 | 25 mm x 15 mm | Confirm the device slot accepts it |
| Mini-UICC (3FF) | ETSI TS 102 221 | 15 mm x 12 mm | Confirm the device slot accepts it |
| 4FF | ETSI TS 102 221 | 12.3 mm x 8.8 mm | Confirm the device slot accepts it |
| MFF1 | ETSI TS 102 671 | Adapted for socketing | Decided in the device design |
| MFF2 | ETSI TS 102 671 | Package layout; large central heatsink possible | Decided in the device design |
Environmental classes: read the class string, not the word "industrial"
ETSI TS 102 671 gives the M2M UICC a classification string such as TA-...-RA, with letters for temperature, moisture/reflow, humidity, corrosion, vibration, shock, data retention and minimum updates. The card stores these classes in a file called EF ENV-CLASSES, so a supplier can state them precisely.
For example, the temperature classes run from TS (-25 to +85 C) to TC (-40 to +125 C); data retention classes RA, RB and RC mean 10, 12 and 15 years from manufacture; VA and SA refer to automotive vibration and shock tests. Match the classes to the enclosure and installation, and ask for the class string of the exact card you are offered instead of relying on a generic "industrial grade" label.
| Class | Operational and storage range |
|---|---|
| TS | -25 C to +85 C |
| TA | -40 C to +85 C |
| TB | -40 C to +105 C |
| TC | -40 C to +125 C |
Where eSIM fits
GSMA describes eSIM as a way to download the SIM securely into a secure element permanently embedded in a device, with security equivalent to the removable card. Its IoT specification is designed for devices that are network-constrained or have little or no user interface, and SGP.32 covers remote provisioning and management of the eUICC in such devices.
An embedded eUICC still has a physical format and environmental properties, and the remote workflow depends on the device, the eUICC and the service supporting the same specification. Compare the two delivery models in our physical SIM versus eSIM framework before deciding.
What to confirm before ordering
Bring the device facts first, then ask the supplier to confirm the card and subscription facts. Quanqiu IoT confirms card format, eSIM workflow and specifications per project; the catalog shows 1 GB reference prices by destination and is a starting point, not a statement of card class or coverage.
- Record the device slot or embedded format (2FF, 3FF, 4FF, MFF1 or MFF2).
- Describe the installation: temperature range, humidity, vibration and expected service life.
- Ask for the card environmental class string and compare it with the installation.
- If eSIM is required, ask which GSMA eSIM specification and version the device and service support.
- List countries, monthly data and the management functions you need, then request a pilot.
Frequently asked questions
Is an IoT SIM different from a phone SIM?
Physically it can use the same removable formats. The difference lies in the subscription, the intended machine use and, for M2M UICCs, optional environmental classes and form factors defined by ETSI TS 102 671. Ask which of these a specific offer includes.
What is an MFF2 SIM?
MFF2 is one of two machine-to-machine form factors defined in ETSI TS 102 671. It is a package layout specified for integration in the device design, so it is chosen with the device or module maker.
Which temperature class do I need?
It depends on the enclosure and installation. ETSI TS 102 671 defines TS (-25 to +85 C), TA (-40 to +85 C), TB (-40 to +105 C) and TC (-40 to +125 C); ask for the class of the exact card offered.
Official references
- 3GPP TS 22.368 version 13.2.0 (ETSI TS 122 368 V13.2.0, 2017-01) Service requirements for Machine-Type Communications (MTC); Stage 1
- ETSI TS 102 221 V18.0.0 (2023-05) Smart Cards; UICC-Terminal interface; Physical and logical characteristics
- ETSI TS 102 671 V16.0.0 (2022-11) Smart Cards; Machine to Machine UICC; Physical and logical characteristics
- GSMA: What is an eSIM? Guide to eSIM technology and use cases
- GSMA SGP.32 v1.2 overview
Related reading
More insights
Send your device slot or module type, installation conditions, countries and expected data use to Quanqiu IoT to confirm a suitable SIM format and plan.
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