What Is the Difference Between 2FF, 3FF and 4FF SIM Card Connectors?
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- Sep 4,2026
2FF (Mini SIM, 25×15mm), 3FF (Micro SIM, 15×12mm) and 4FF (Nano SIM, 12.3×12.3mm) all share the identical C1-C8 electrical contact definition — only the plastic card outline and the socket cavity change.
SIM Form Factor Comparison
| Form Factor | Size | Common Name | Connector Match |
|---|---|---|---|
| 2FF | 25 × 15 mm | Mini SIM | Full-size SIM socket, ID-1 derived carrier |
| 3FF | 15 × 12 mm | Micro SIM | Micro SIM socket with 3FF card holder |
| 4FF | 12.3 × 12.3 mm | Nano SIM | Nano SIM socket, lowest profile designs |
All three keep the identical C1-C8 electrical contact definition — only the card's plastic outline and the socket cavity change. This is why a smart card connector's pin count (6-pin or 8-pin) is independent of the form factor it accepts.
Choosing by Form Factor
- 2FF sockets remain common in industrial terminals, payment devices and automotive telematics where card robustness matters.
- 3FF and 4FF sockets dominate IoT modules and consumer devices, and are typically available in heights from 1.00 mm to 2.00 mm.
- Mixed 2FF/3FF/4FF combo sockets exist for devices that must accept multiple card sizes without adapters.
Our C1-C8 pin function reference covers the electrical mapping across all form factors; browse card connector options for socket availability.