Despite the fact that it isn't being sold in that many markets, it's now time for the Samsung Galaxy S6 Duos to get its taste of the absolute latest version of Android, namely 5.1.1 Lollipop.
As you can see from the screengrab to the left, in the case of the dual-SIM Galaxy S6 Duos, the download will be around 620MB in size if you choose to apply the update over-the-air.
You can obviously do that, but if for some reason you don't get the update notification on your phone, you can always turn to Kies, Samsung's desktop PC app, for help. You should be able to install the new software using it too.
For now, the rollout seems to be confined to Dubai, the United Arab Emirates. However, it's sure to spread to other markets soon.
Just as the changelog in the screenshot notes, aside from bumping up the Android version, the new software also brings with it some unnamed security enhancements, improved UI and system stability, and performance improvements.