Google released Android 4.4-r1.2 Factory images, binaries, AOSP – Bug fixes for Nexus devices
After the debut of Android 4.4 KitKat like few days ago Google release the Android 4.4-r1.2 KRT16s KitKat. This is a bug fixes update. The old build KRT16o was removed all through out and replaced by build KRT16s. To date many are still waiting for an OTA update and seems the KRT16s will be pushed for all devices instead of KRT160 to Nexus 4, Nexus 5, Nexus 7 2012, Nexus 7 2013, Nexus 10.
List of Factory images (KRT16s) and can be use to flash your device to Android 4.4-r1.2.
Nexus 5 “hammerhead”(GSM/LTE)
Nexus 7 “razor”  (Wi-Fi)
Nexus 7 “razorg” (Mobile)
Nexus 10 “mantaray”
Nexus 4 “occam”
Nexus 7 “nakasi”  (WiFi)
Nexus 7 “nakasig” Mobile
You will find these files useful if you have used the Android Open-Source Project, flashed custom builds on your device, and wish to return that device to its factory state.
In order to use these files, you need to have the
fastboottool in your PATH. That tool is compiled as part of every configuration of the Android Open-Source Project and is the tool used to flash custom builds on your device. On GNU/Linux systems, this also implies that you have configured USB access as mentioned in the machine setup instructions.
Your device needs to be in fastboot mode, with the bootloader unlocked. The relevant key combinations and commands are documented on the page about building for devices.
You need to uncompress each download before use, which creates a new directory for that exact download. That directory contains a
./flash-all.shscript, which handles the various operations, installs the necessary bootloader, baseband firmware(s), and operating system. Note that this operation deletes all user data by default. – Google Developer