SIM [subscriber identity module] cards was introduces in 1991. This first model, aka FF1, have 85.60 x 53.98mm [just similar with credit card size]... I remmember one of my first GSM cellular phone [Motorala something] was compatible with this FF1 SIM.
Anyway, during the time, new [smaller] SIM models was introduced, but keeping compatibility with previous ones.
To make the long story short and to have further reference, read: SIM formats.
Modular modems [c-uGSM, h-nanoGSM, d-u3G and l-LTE] SIM support:
- 2FF [STANDARD/MINI] SIM/USIM
- 1.8V or 3V compatible
Full size modems [a-gsm, a-gsmII and b-gsmgnss] SIM support:
- 2FF [STANDARD/MINI] SIM/USIM
- 1.8V or 3V compatible
Universal modems and boards familly[u-gsm and xyz-uGSM] SIM support:
- 4FF [NANO] SIM/USIM
- 1.8V or 3V compatible
HINT:
4G/LTE [for l-LTE or for LTE universal modems familly], 3G [for d-u3G or for 3G universal modems familly] or GPRS services must be enabled to your SIM subscription and to be available in your area. Check those with your MNO [mobile network operator].