Steve announced that the iPad 3G would use micro SIMs/3FF cards as oppose to traditional SIMs. So what are micro SIMs and how do they differ from the typical SIMs people have been using for ages? Well, according to the European Telecommunications Standards 
Institute (ETSI), the folks that sets the standards for SIM cards, It turns out that micro SIMs are identicalelectronically to their older bigger counterparts. In other words, the only difference between Micro SIMs and traditional SIMs is the size of the plastic holding that gold-colored contact (About 52% smaller). So essentially, that means one can simply trim down a typical SIM card to the size of a micro SIM and it will just work in a micro SIM device such as the iPad.
If that’s the case, this is old news to the people who uses ‘Dual SIM‘. They basically trim down the 2 SIM card anyway to micro SIM size and slide it in a dual SIM adaptor.
AT&T will obviously be offering micro SIMs for the iPad here in the states. So is T-Mobile in partnership with Lok8u. And outside of the US, O2, Orange and DoCoMo are also stocking up on micro SIMs.
[via CNET UK, The Register]
Micro Sim = iSim