Gapps 6.0.1 -

Android 6.0.1 Marshmallow (released late 2015) brought Now on Tap, granular app permissions, and Doze mode. But if you flashed a clean AOSP-based ROM like CyanogenMod 13 or Resurrection Remix, you got… a bare-bones OS. No Play Store. No Gmail. No Maps. Just a functional, Google-less ghost.

GApps packages are highly modular, allowing users to choose how much Google "bloat" they want on their device based on storage capacity and performance needs. Gapps 6.0.1

Your /system partition is too small. Fix: Android 6