Apple started a new trend when it introduced the micro-SIM card found in the Apple iPhone 4 and the iPad 3G. Like a regular SIM, the micro-SIM holds the necessary subscriber information while losing some of the plastic border. Apple says that the smaller cards make more room for a larger battery, but they also come with a couple of trade-offs. For example, the smaller size means that the micro-SIM won't fit into a standard card slot an vice versa.
Leave it to the marketplace, however, to come up with solutions. We've already told you about a tool that will shave a regular SIM down to size, but you also can buy an adapter that will give a micro-SIM the extra girth it needs to fit into another phone. We ordered one from BuyMicroSIMadapter.com and tested it with an iPhone 4 micro-SIM.
The process is about as easy as you'd expect. Just snap the micro-SIM into the tiny plastic tray and and insert the whole thing into your alternate handset. We used it with a Samsung SGH-A177 and didn't encounter any problems with registering the micro-SIMm and making calls. We'd recommend an adapter for any iPhone owners who may want to use other handsets occasionally while retaining their phone number.