Google today released the Android 5.0 Lollipop factory images for the Nexus 9 and the Nexus Player, the only two devices that are running Lollipop and available to the public at the moment.
The factory image will allow Nexus 9 and Nexus Player owners to restore their device back to stock in case they somehow manage to bork it. The build version of Android 5.0 in the factory images is the same as the Lollipop build shipping in the retail units of both devices: LRX21L. Do note that flashing a factory image will require you to unlock the bootloader of your Nexus device first.
Since the LTE variant of the Nexus 9 is yet to go on sale, its factory image is also not yet available for download. The tablet, however, crossed the FCC only earlier this week, which means it should pop up on the Google Play Store sometime soon.[Via Google Developers]