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    Dec, 15 2020

    SIM Form Factors Explained

    Quick definition: SIM form factors are the standardized sizes subscriber identity modules (SIMs) are manufactured in. There are five SIM form factors: 1FF, 2FF, 3FF, 4FF, and MFF2. Each generation of SIM is smaller than the last.

    Iot Glossary
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    The capabilities of each form factor are the same, but they each have different dimensions, which makes them more suitable for specific kinds of devices. 2FF, 3FF, and 4FF SIMs have to be inserted into a device, while MFF2 SIMs have to be embedded—which is why they’re also called eSIMs. (1FF SIMs are no longer in use.).

    If you’re building a device that relies on cellular connectivity, you need to understand the various SIM form factors available, so you can make the best choice and design accordingly. We’re going to get into the specs and compare the various form factors, but first, let’s look at why businesses use SIMs in the first place.

    The advantage of SIMs

    As a business, you have a range of technologies and protocols to choose from to enable machine-to-machine connectivity. Which one you use greatly depends on the use case. For example, smart home connectivity is mostly provided via Bluetooth variants, while logistics and transportation utilize cellular M2M connectivity.

    Global coverage

    For large-scale, global deployments, cellular M2M connectivity is generally considered the most reliable and beneficial connectivity method. You don’t need to build new infrastructure for every new deployment—you just have to connect to a network that’s already in place. As you deploy in new countries, your cellular provider may have roaming agreements with another carrier that covers that region. If not, you can select a new carrier with local coverage. 

    Cellular is a WAN (wide area network) with the long-range ability to connect globally using radio waves that are sent and received via cell towers. In comparison, WiFi connectivity requires your device to remain much closer to the access point/router, preventing long-range mobility. Similarly, Bluetooth connectivity is also short range, requiring your device to be within 10–100 meters of the access point, depending on the power-class.

    Built-in authentication

    Cellular networks use SIM cards to authenticate devices, associate them with a legitimate subscriber, and provide secure connectivity. Hackers can spoof IP addresses, but they can’t spoof a subscriber’s identity, which is stored on a SIM card.

    Secure connectivity

    When your device connects to a customer’s WiFi, it shares the connection with all the other devices on the WiFi network. If these devices have a security issue, it puts your devices at risk—and the inverse is true, too. Connecting to a cellular network keeps your devices separate from your customers’ other Internet-connected devices. Manufacturers need to take IoT security seriously, and cellular connectivity gives you a number of security advantages, starting with the network your devices connect to.

    If cellular connectivity is the right choice for your business, the next question is: what SIM card is best suited to my business needs? Let’s take a look at some of the design options and what you should consider when choosing a form factor.

    Which SIM form factor is best for your business?

    SIM cards come in four standard sizes or forms, ranging from 1FF, the first and largest SIM to be developed, to 4FF or nano-SIM, the latest and smallest in SIM design technology. (The 1FF isn’t used in modern SIM applications.) There is also an embedded SIM option—the MFF2.  

    Each generation of SIM has been smaller than the last. While they’re usually referred to by the generation they come from (1, 2, 3, 4), later SIMs are also called “mini SIMs” (2FF), “micro SIMs” (3FF), “nano SIMs” (4FF), and “eSIMs” or “embedded SIMs” (MFF2). 

    Note: MFF2 stands for machine-to-machine form factor.

    Here are the dimensions of each form factor:

    1FF: 85.6mm × 53.98mm × 0.76 mm
    2FF (Mini): 25mm x 15mm x 0.76mm
    3FF (Micro): 15mm x 12mm x 0.76mm
    4FF (Nano): 12.3mm × 8.8mm × 0.67mm
    MFF2 (eSIM): 5mm x 6 mm x 1mm

    Let’s take a closer look at the SIM form factors that are currently in use today.

    2FF, 3FF, 4FF SIMs

    As you can see below, the actual module within the SIM card is identical—the packaging just gets smaller—which is why the form factor doesn’t impact a SIM’s capabilities.

    SIM comparison 2

    The SIM form factor you select is completely dependent on the size of your device and the amount of space you have to accommodate a SIM. For example, collar animal tracking collars may use a nano SIM (4FF), whereas larger devices such as GPS systems used in fleet management companies could accommodate a larger form factor.

    It’s also possible to select industrial-grade SIMs in the form factors 2FF–4FF. These M2M SIMs are more durable than traditional SIMs, and they’re designed to meet the requirements of your M2M deployments. They come with a thicker pin plate to safeguard your device from corrosion, vibrations and other environmental factors, such as extreme temperature conditions. Typically, industrial-grade SIMs can withstand temperatures between -40°C and +105°C.

    To accommodate one of the 2FF–4FF SIMs, you need to physically have a SIM portal incorporated into your device’s design, which can change the aesthetic. An alternate option to the 2FF–4FF SIMs is the MFF2 embedded SIM. This SIM has several benefits that directly address the issues of aesthetics and robustness as well as other provisioning capabilities.

    Embedded SIM

    SIM comparison

    Embedded SIMs (often referred to as eSIMs) are the most common choice for M2M applications because they come vacuum sealed and can be soldered directly onto your device’s circuit board. This increases reliability by reducing malfunction due to shocks, corrosion, and other environmental factors. Additionally, the lifecycle of an embedded SIM is up to 17 years—much longer than standard form factors. With an eSIM, the module will likely outlast the device.

    Another critical benefit of embedded SIMs is physical security. Soldering the SIM directly onto your device’s circuit board makes it impossible for anyone tampering with your device to remove the SIM for misuse

    What about eUICCs?

    An Embedded Universal Integrated Circuit Card (eUICC) is a component that can be installed on any SIM form factor. Since they’re embeddable, and consumer devices like smartphones will always install them on MFF2s, you’ll often hear eUICC and eSIM used as synonyms. But not every eSIM has an eUICC, and not every eUICC is installed on an eSIM.

    Make the right selection for your application 

    The most effective way to ensure you make the best decisions for your business is to keep yourself informed about all the options available to you. To help you quickly identify the benefits and differences of each SIM form factor, we have included an assessment table below:


    In terms of the best SIM for your cellular M2M connectivity solution, we have exemplified the advantages of an embedded SIM over a regular form factor (2FF–4FF). An embedded solution offers a longer lifecycle, better security, greater durability, and more flexibility for your device’s design.

    Whatever form factor you decide is right for you, we can provide it for you. At EMnify we specialize in cellular M2M connectivity. If you have any questions about SIM form factors or the best connectivity solution for your business, our team is always happy to help and offer advice.

    Tobias Weber

    Tobias Weber

    More than six years of experience as a senior editor in the realm of smart home, connectivity and Internet of Things. And still as curious as on the first day.

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