Are you tired of your MIUI on your Mi 4 or Mi 3? Here's some good news for you, CyanogenMod 12.1 Nightlies is now officially available for both the devices. You'll get the latest version of Android with this latest ROM. But as it;s nightlies, so it won't be as stable as stable releases.
Head over to the below source and get all the instructions to download the files and to see the installation procedure.