Asus has begun rolling out a system update for both the Zenfone 4 and Zenfone 5. The updates are available over-the-air (OTA) and are 38 MB / 58 MB in size. The update addresses stability on both the phones and is just a housekeeping update. Asus has said that the new Zenfone series is upgradable to Android 4.4 KitKat, so we will be waiting on that front as well.
We recently did the unboxing of the Zenfone 4 and the Zenfone 5, which you can see below.
