> For the complete documentation index, see [llms.txt](https://docs.monogoto.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.monogoto.io/getting-started/sim-cards/embedded-sims.md).

# Embedded SIMs

<figure><img src="/files/uPVRaH6F8kXrSjP6Y8oY" alt=""><figcaption></figcaption></figure>

### Description

An embedded SIM (eUICC) is a SIM that is soldered directly onto the device's circuit board instead of being inserted as a removable card. There is no tray and no socket, which removes mechanical points of failure, resists dust and vibration, and lets the SIM be sealed inside the device for its full lifetime. The same Monogoto connectivity, coverage and platform features apply across every embedded form factor, what changes between them is the physical package and footprint.

Embedded SIMs are the right choice for IoT devices that ship in volume, operate in harsh environments, or move between cities and countries.&#x20;

### Choosing a form factor

We offer embedded SIMs in two soldered form factors.&#x20;

They are functionally identical the decision is driven by the space available on your board.

|                        | MFF2                           | MFF4                                                    |
| ---------------------- | ------------------------------ | ------------------------------------------------------- |
| Package                | VQFN-8-4                       | USON-8-6                                                |
| Size (mm)              | 6 x 5                          | 2 x 2                                                   |
| Footprint              | \~30 mm²                       | \~4 mm² (≈87% smaller)                                  |
| Pins                   | 8 (no-leads)                   | 8 (no-leads)                                            |
| Network technologies   | 2G/3G/4G/LTE-M/NB-iot          | 2G/3G/4G/LTE-M/NB-iot                                   |
| Operating temperatures | -40°C to 105°C                 | -40°C to 105°C                                          |
| Best for               | General IoT, modules, gateways | Space-constrained devices: wearables, trackers, e-bikes |

In short, choose **MFF2** as the established, widely supported default, or **MFF4** when board space is at a premium and you need the smallest possible discrete SIM.