Users must have 2GB of free space to download and install the update as the update weighs 1.1GB. Since the update is being rolled out over-the-air, it may take some time before it comes to your device. One can also manually check for the update by going to Settings ->About Phone -> Software Update.
Asus Zenfone 2 ZE551ML and Asus Zenfone 2 ZE550ML were launched in April last year in India. The Zenfone 2 ZE550ML has only 16GB of internal memory and it has an expandable storage slot as well that can hold a micro SD card of up to 64GB capacity, while the Zenfone 2 ZE551ML comes in 32GB and 64GB inbuilt storage models. Asus Zenfone 2 ZE551ML model has a 5.5 inch touchscreen with Gorilla Glass 3 and full HD resolution while Asus Zenfone 2 ZE550ML has a 5.5-inch screen HD resolution. Both have 13 megapixel primary camera, 5 megapixel rear camera and 3000 mAh battery.
Asus Zenfone 2 ZE551ML has 4GB RAM and it comes with 64-bit Intel Atom Z3560 1.8 GHz quad core processor. It has a 128GB internal memory model as well that has Intel Atom Z3580 2.3 GHz quad core processor.