+**4ff** designates Form Factor 4, representing the [Nano-SIM](/wiki/Nano-SIM) card. This is the smallest physical iteration of a [SIM card](/wiki/SIM_card), essential for modern mobile devices. Its compact design allows for ever-slimmer electronic products.
+## See also
+- [Micro-SIM](/wiki/Micro-SIM)
+- [Mobile Phone](/wiki/Mobile_Phone)
+- [Cellular Network](/wiki/Cellular_Network)
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