Mac OS X Public Beta was the first publicly available version of Apple Computer's Mac OS X operating system to feature the Aqua user interface. It was released to the public on September 13, 2000, for US$29.95. Its release was significant as the first publicly available evidence of Apple's ability to ship the "next-generation Mac operating system" after the Copland failure and the exploratory Rhapsody that was only ever available to developers. It allowed software developers and early adopters to test a preview of the upcoming operating system and develop software for it before its final release. It is the only public version of Mac OS X to have a code name not based on a big cat until the release of 10.9 Mavericks in 2013. The US version had a build number of 1H39 and the international version had build number 2E14.