Differences between SIM types - which SIM to choose?

Cellular connectivity is the most reliable and widespread connectivity method for IoT (Internet of Things) and M2M (Machine-to-Machine) devices, but in order to identify 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 device's purpose, functionality and space available to host a SIM card or chip. 
In total, there are 4 types of SIMs that also mark the technological evolution:
  •  SIM card
SIM card comes in four form factors or sizes - 1FF, 2FF, 3FF and 4FF. However, the 1FF option is not in use anymore in 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.
  •  MFF2 UICC (chip SIM)
There is another option, an embedded SIM called MFF2 UICC (chip SIM), which from a technical perspective, works in a same way as a regular SIM card, but is vacuum sealed and can be soldered directly onto the circuit board during fabrication. 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 just need longer lifecycle. Additionally, chip SIM is permanently deployed in the device and cannot be removed for misuse, making it more secure. 
  •  eUICC (eSIM) - future of SIMs!?
There is a lot of talk in the industry about embedded SIMs. However, it's important to not mix up MFF2 UICC (chip SIM) with eUICC solution (eSIM). They come from different eras and work quite differently. Like chip SIM, eSIM can be soldered onto the circuit board, but it can come in the form of a 2FF, 3FF or 4FF SIM card as well. eSIM can be regarded as one possible future technology, deployed already in some newer smart devices (e.g. Samsung Gear 2 watch). While maintaining the same form factors (SIM card and chip SIM), eSIM solution follows a new standard, which makes switching between mobile carriers much easier. Please read further about eSIM from our other blog post here.  
  •  Soft SIM
    With soft SIM technology, there is no SIM deployed in the device. The magic happens purely in software. It is too early to say whether soft SIM solution goes into mass market as some market players claim soft SIMs to be too exposed to hacking.

    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 (UICC/eUICC) 6mm × 5mm × 0.9 mm (0.236" x 0.196" x 0.035")

    1oT service supports SIM cards (2FF - 4FF), MFF2 UICC (chip SIMs) and will soon support eUICC(eSIM) as well. Read more from here or contact our team at hello[at]1oT.mobi.

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