What Sim is That?
Published:  12 May 2017

We all know that SIM cards come in a number of different sizes. But how does each SIM card differ and what do they look like?

A note about terminology

Correctly speaking, these cards are officially known as a UICC   (Universal Integrated Circuit Card), and the SIM (Subscriber Identity Module) for a 2G network (and USIM for a 3G/LTE network) are now applications that are run by the microprocessor in the card. But for the purposes of this Tip, we will refer to UICC as a SIM to match the general use of the term SIM.

The SIM family tree


SIM Card form-factors to scale. SIM images © Sierra Wireless Ltd
SIM Card form-factors to scale. SIM images © Sierra Wireless Ltd


 Standard Name   Common Name   Dimensions (mm) 
1FF Full Size 85.6 x 53.98 x 0.76
2FF Mini SIM
Standard SIM
25 x 15 x 0.76
3FF Micro SIM 15 x 12 x 0.76
4FF Nano SIM 12.3 x 8.8 x 0.67
MFF2 Embedded SIM
SON-8 IC Footprint
6 x 5

1FF or Full Size card

In the beginning was the Full size SIM card - also known as 1FF (1st Form Factor). This was the size of a standard Credit Card (85.6 x 53.98 mm)

The 1FF cards are rarely used in mobile equipment any more (excepting some Satellite and security modules) - but the other (smaller) size SIM cards are often supplied embedded in a full-size card as a push-out module.

2FF or Mini SIM card

This size SIM card is what is usually recognised as the standard SIM card today.

The MangOH Green and FX30 modules from Sierra Wireless use a Mini SIM card as the primary SIM.

3FF or Micro SIM card

In response to size contraints in the mobile phone market, the 3FF or Micro SIM card is the 2FF SIM card with less plastic flashing around the edges.

With care (although this is not recommended) it is possible to cut down a 2FF SIM card to fit into a device that uses a 3FF SIM card.

The MangOH Red module from Sierra Wireless requires a Micro SIM card as the primary SIM.

4FF or Nano SIM Card

The 4FF or Nano SIM card has the same contact layout as the 1FF, 2FF and 3FF cards, but the contact area (and thickness) has been reduced so that the overall size and volume of the card could be reduced.

There are adapters available ot fit a 4FF card into modules that require a 2FF or 3FF card, but extreme care should be taken to ensure that the SIM or adapter do not jam in the larger card enclosures.

MFF2 embedded SIM card

The MFF2 format SIM is a surface mount integrated circuit device that is soldered onto the module board at production time and is not user changeable as are the other (removable) SIM cards.

Being soldered to the module board increases both reliablity and SIM security, but has the downside that it is difficult (if not impossible) to change service providers once the SIM has been installed. This issue of portability is currently being addressed by enabling remote SIM provisioning systems (depending on Telco support).

The Multisize SIM

As all form factors have common contact positions and are size subsets of eachother, many Telcos or service providers ship a single 1FF size card with partial cutouts around each smaller size card so that the user simply pushes out the appropriate size SIM for their device.

While this saves the service provider inventory and stocking costs, it is not always the best solution for end users - M2M devices in particular. When using a 2FF card that has smaller cards partially cut out, it is possible (probable?) that the smaller, inner cards can fall out while inserted in the device.

If at all possible, when ordering cards from your service provider, try to order the appropriate size cards for your devices, rather than using the multi-fit cards that will probably be supplied by default.