Asus Zenfone 2 ZE551ML


The Asus Zenfone 2 ZE551ML, introduced in early 2015, marked a significant step forward for Asus in the smartphone market. It was one of the first smartphones to offer 4GB of RAM, making headlines for its performance capabilities. The Zenfone 2 was aimed at providing a high-end experience at a mid-range price point.


  • Operating System: Initially launched with Android 5.0 Lollipop, with ZenUI skin on top.
  • Display: 5.5-inch IPS LCD capacitive touchscreen with a resolution of 1080 x 1920 pixels.
  • Processor: Quad-core Intel Atom Z3580 (for the 4GB RAM version) or Z3560 (for the 2GB RAM version).
  • Memory: Options of 2GB or 4GB RAM, with 16/32/64 GB internal storage, expandable via microSD up to 256 GB.
  • Camera: 13 MP rear camera with dual-LED flash and a 5 MP front camera.
  • Battery: 3000 mAh non-removable battery with fast charging capabilities.
  • Connectivity: Wi-Fi 802.11 a/b/g/n/ac, Bluetooth 4.0, NFC, and GPS.
  • Other Features: Dual SIM support, FM Radio, and Asus’s custom ZenUI skin.


  • Performance: The 4GB RAM variant, in particular, was a powerhouse in terms of multitasking and overall performance.
  • Value for Money: Offered flagship-like specifications at a mid-range price.
  • Expandable Storage: The inclusion of a microSD slot was beneficial for users needing more storage.
  • Fast Charging: The device supported fast charging, allowing for quicker top-ups.
  • Customizable ZenUI: Asus’s skin had a range of customization options and added features.


  • Bulky Design: Some users found the phone a bit thick and heavy.
  • ZenUI Bloatware: While ZenUI was customizable, it came with a number of pre-installed apps that not everyone found useful.
  • Average Battery Life: Despite its size, the battery could struggle to last a full day with heavy use.
  • Rear Volume Buttons: The placement of the volume buttons on the back was divisive; some loved it, while others found it inconvenient.

Comparisons to Other Technologies:

In 2015, the smartphone market was evolving rapidly. The Zenfone 2 faced competition from:

  • OnePlus One: Known as the “flagship killer”, it offered high-end specs at a similar mid-range price point.
  • Moto G (3rd Gen): Motorola’s offering in the mid-range segment, known for its clean Android experience.
  • Samsung Galaxy A7: A mid-range offering from Samsung with a premium design.

Launch Date:

The Asus Zenfone 2 ZE551ML was announced in January 2015 and released in March 2015.
Common Issues/Problems:

  • Software Bugs: Some users reported bugs and glitches with ZenUI, especially with early versions.
  • Overheating: There were occasional reports of the device getting warm, particularly during intense tasks or prolonged gaming.
  • Battery Drain: Some users experienced faster than expected battery drain, possibly due to software issues.


The Asus Zenfone 2 ZE551ML was a significant offering in the mid-range segment in 2015. It pushed the boundaries of what consumers could expect at that price point, particularly with its 4GB RAM variant. While it had its flaws and faced stiff competition, it was a testament to the evolving smartphone landscape, where high-end features were becoming accessible to a broader audience.

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