Version 6.1 of Apple’s iOS operating system adds LTE capabilities to 36 additional iPhone carriers and 23 additional iPad carriers around the world. Available as a free software upgrade, it is compatible with the iPhone 5, 4S, 4, and 3GS; the third and fourth generation iPads, iPad mini, and iPad 2; and the fourth and fifth generation iPod touch. Some features may not be available on all products. Specifically, LTE is available on the iPhone 5, iPad mini, and fourth generation iPad Wi-Fi + cellular models through select carriers. Network speeds depend on the carrier networks.