Microsoft has just released the build 10586 preview version of Windows 10 Mobile to the members of the Windows Insider Program who have signed up to get updates in the Slow ring. This build was released earlier this week for Fast ring members.
As we previously reported, build 10586 is mainly for fixing bugs and putting in some improvements to Windows 10 Mobile. It's also the same build that's available in Microsoft's Lumia 950 and Lumia 950 XL smartphones.
Source: Gabriel Aul (Twitter)