In recent weeks, Sony has reportedly begun rolling out the current Android 5.1.1 Lollipop operating system to a host of models including the previous flagships Xperia Z1, Z1 Compact, and Z Ultra. It even treated mid-range devices such as the Xperia C3 and T2 Ultra with the new upgrade.

It now appears that the Japan-based device maker is also working to deliver the said OS to another mid-range lineup, 2014's Xperia M2, M2 Dual and M2 Aqua. XperiaBlog.net, a Sony watchdog site, recently shared that Android 5.1.1 Lollipop with build number 18.6.A.0.175 has just been certified by the PTCRB. The PTCRB is an agency that operates a certification program for devices issued by North American operators.

The site reported that the firmware is bound for the Sony Xperia M2 with model numbers D2303, D2305 and D2306, Xperia M2 Dual (D2302), and Xperia M2 Aqua (D2403, D2406). This means that all variants of the said handsets are slated to jump from their current Android 4.4.4 KitKat directly version 5.1.1 Lollipop.

When Google's Android 5.1.1 OS arrives to the Xperia M2 line, it will carry over improvements such as an updated Bluetooth and Wi-Fi Quick Settings, a fix for reported memory leak issues, and more importantly, a solution to the dangerous Stagefright vulnerability.

Sony's Xperia M2, M2 Dual, and M2 Aqua essentially have the same features and specifications. The only difference is that the M2 Dual is only model among them to provide dual-SIM support and the M2 Aqua is the only one to sport an IP68 certification, making it dust- and waterproof.

The handsets all pack 4.8-inch displays with 540 x 960 pixels, resulting to a decent 229ppi pixel density. A 1.2 GHz quad-core processor is fitted inside coupled with 1 GB of RAM and 8GB or built-in storage. They were originally released last year running Android 4.3 Jelly Bean but have since been updated to version 4.4.4.

All three models have an 8-mgepixel autofocus camera with LED flash at the back and VGA camera in front. They pack a non-removable lithium ion battery with 2,300mAh capacity.

The release of a PTCRB certification typically signifies that a new firmware's consumer distribution is not too far away. Once these Android 5.1.1 Lollipop updates arrive to the Xperia M2, M2 Dual, and M2 Aqua, they will fulfill Sony's promise back in June that it will release software updates to all of its recent models.