SIM Cards come in all shapes and sizes. This article will explain how each SIM card differs from the other.
2FF or Mini SIM card
This size SIM card is what is usually recognized as the standard SIM card today.
3FF or Micro SIM card
In response to size constraints in the mobile phone market, the 3FF or Micro SIM card is the 2FF SIM card with less plastic flashing around the edges.
4FF or Nano SIM Card
The 4FF or Nano SIM card has the same contact layout as the 2FF and 3FF cards, but the contact area (and thickness) has been reduced to reduce the overall size and volume of the card. 
MFF2 embedded SIM card
The MFF2 format SIM is a surface mount integrated circuit device soldered onto the module board at production time and is not user-changeable, as are the other (removable) SIM cards.
MFF2 Embedded SIM
SIM Card form factor dimensions
By dimensions, SIMs measure accordingly:
- 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 (chip SIM) 6mm × 5mm × 0.9 mm (0.236″ x 0.196″ x 0.035″)