iPhone 5 confirmed to use nano-SIM, current SIMs not compatible
 

While Apple was busy announcing the iPhone 5, it left out mention of whether the device would use the recently approved (and Apple-designed) nano-SIM standard. Sure enough, the leaks were right once more -- Apple is relying on that even tinier subscriber module for GSM, HSPA and LTE networks. The company also makes clear that there's no going back, so you'll have to chuck your earlier micro-SIM card if you've got one. Such is the price of progress.

http://www.engadget.com/2012/09/12/i...ot-compatible/