However, the update deployed to OnePlus 2 devices is just a hotfix that's suppose to address a problem with the smartphone's network reception. If you haven't yet upgraded to a newer OnePlus smartphone, then you should be looking for OxygenOS 3.5.6 software update.
As mentioned, the update should fix persistent network drops that many OnePlus 2 owners have been complaining of for quite some time now. Other than that, there aren't any new features or improvements included in the update.
According to OnePlus, OxygenOS 3.5.6 Hotfix OTA is delivered in stages, which means it will initially be available to a small percentage of OnePlus 2 owners. However, the Chinese company promises to get everyone covered as fast as possible.
One other thing mentioned by OnePlus is related to another issue affecting OnePlus 2 phones. Apparently, the company is now working on a fix for those users affected by the IMEI loss issue, but an ETA hasn't been given yet, so stay tuned for more on this one.