Microsoft has now pushed Windows 10 Mobile Build 14393 to Insiders in Slow Ring. Earlier Microsoft pushed the Build 14393 to Insiders in Fast Ring and many consider it to be the RTM Build. You can read the official changelog and known issues of the Build by clicking here and here.
Usually Builds that enjoy good Insider Feedback make their way to Slow Ring. We have posted hands-on demo and impressions of the Mobile Build 14393 and you can read it by clicking here.
Microsoft has however not made it clear officially whether Build 14393 is indeed the RTM build and we will keep you updated if we come to now more about it.