Google has just released the Developer Preview builds of Android M for the Nexus 5, Nexus 6, Nexus 9 and the Nexus Player on its website.
Android M is the upcoming version of Android that focuses on polish and quality. Google has fixed thousands of bugs in the OS and aims to make it more battery efficient.
The final version of Android M will be released in Q3 of 2015, but until then, Nexus 5, Nexus 6 and Nexus 9 (Wi-Fi) owners can flash the developer preview on their device to get a taste of Android M.
Android M developer preview image