The upgrade is for all devices including iPhones (3GS, iphone4, iphone4s. iPads both models and iPod touch that have ios5 installed. If you have an earlier iOS installed then if you use iTunes only the latest version will be installed. If you use OTA upgrade the file size is small and takes about 5 minutes however if you upgrade via iTunes it in fact is a full install not just an upgrade. You must be connected to a power source to use OTA and I suggest as a precaution make sure you are backed up first before upgrading.