Differences between SIM types - which SIM to choose?

Tags: IoT
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Märt Kroodo

Cellular connectivity is the most reliable and widespread connectivity method for IoT (Internet of Things) and M2M (Machine-to-Machine) devices. In order to connect a device to a carrier, it needs a Subscriber Identity Module, or as most people call it, a SIM. The size and type of SIM you need to select depends on the device's purpose, functionality, and space available to host a SIM card or chip.

There are mainly two different SIM technologies and four form factors used today.

SIM card (UICC)

This SIM card comes in four form factors or sizes - 1FF, 2FF, 3FF and 4FF. However, the 1FF option is not in use anymore for modern devices. All other types, from 2FF to 4FF, are still dominating the cellular connectivity world. These SIMs are widely accessible, relatively easy to operate with, and well supported by hardware components.


There is another option, an embedded SIM called MFF2 UICC (chip SIM), which, from a technical perspective, works in the same way as a regular SIM card but is vacuum-sealed and can be soldered directly onto the circuit board during manufacturing. This makes the chip SIM a perfect option for devices that are located outdoors (can be sealed and protected from corrosion), are in constant motion (shocks), or require a longer lifecycle. Additionally, chip SIMs are permanently installed in the device and cannot be removed for misuse, making it more secure.


eSIM is the future of SIM cards, using a completely different technology.

It is a common mistake to refer to an embedded chip SIM (MFF2) as an eSIM, but that is not always the case. An eSIM can come in all modern form factors such as 2FF, 3FF, 4FF, and also MFF2.

eSIM is regarded as the future of SIM technology and is already deployed in newer consumer smart devices, and now with 1oT's eSIM solution also in IoT and M2M devices. While maintaining the same form factors, the eSIM solution follows a new standard, which makes switching between mobile carriers much easier thanks to Over The Air(OTA) provisioning. Please read further about eSIM here.

Other SIM technologies

There are other experimental SIM technologies like iSIM, nuSIM, and soft SIM. Many of these come uncertified and are exposed to security threats. A risk that big carriers are reluctant to take.

While every solution has its own benefits, the truly global and interoperable solution is the well known SIM and the new eSIM standard. We have covered many pros and cons of iSIM and nuSIM in our IoT Hacking Series #4 blog post about How do iSIM & nuSIM compare to eSIM?

Form factor dimensions

By dimensions, SIMs measure accordingly:

  • 1FF 85.6mm × 53.98mm × 0.76 mm (3.370" x 2.125" x 0.029")

  • 2FF (mini SIM) 25mm x 15mm x 0.76mm (0.984" x 0.590" x 0.029")

  • 3FF (micro SIM) 15mm x 12mm x 0.76mm (0.590" x 0.472" x 0.029")

  • 4FF (nano SIM) 12.3mm × 8.8mm × 0.67mm (0.484" x 0.346" x 0.026")

  • MFF2 (chip SIM) 6mm × 5mm × 0.9 mm (0.236" x 0.196" x 0.035")

1oT can provide you all the different SIM form factors, and we also have a new eSIM offering.

Read more here or contact our team at hello[at]1oT.mobi.

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