Since we found out the unique size of Apple's 3G iPad SIM card and now know that it requires a micro SIM card (12Ã—15mm) instead of the standard sized SIM card (15Ã—25mm), Mico SIM orders can tell us who the next carriers just might be! Gemalto, a micro SIM manufacturer, today claims that O2 and Orange have been buying up the diminutive cards in their masses. However, the use of Micro SIMs means that, even if the iPad arrives unlocked in the UK, users will be forced to buy the cards from specific mobile operators to ensure 3G connectivity for their device. Unlocked it maybe, but the Micro SIM option means consumers arenâ€™t going to be able to get their iPad online with any old SIM and cheap data deal, but will be forced to opt for whatever Micro SIM contracts operators offer. T-Mobile is also said to have to placed an order in recent times, though the company will likely be unable to carry the iPad in the US.