The Kindle 2 added native PDF capability with the version 2.3 firmware upgrade. Fedora users can upgrade from version to version without reinstalling. Customers could upgrade and retain the same application software. Existing Hotmail customers could freely upgrade to the preview version of Outlook.com and downgrade back. This is not compatible with systems that do not upgrade. More funding changed the plan to upgrade to AH-64C. The Retina models also have fewer user-accessible upgrade or replacement options than previous MacBooks. It will automatically upgrade to WebSocket if possible. The RIM-66J is the version for the New Threat Upgrade. There are no family pack versions of the Anytime Upgrade editions. Regression testing is performed by identifying the changes made to upgrade software. MSC issued requests for proposal to upgrade and refit the ship. Players can also upgrade and customize their weapons and the Nanosuit. The city's infrastructure is stressed by growth and lack of means to upgrade. Players can also upgrade and customize weapons using salvage collected across the island.