New Windows 10 builds in the Fast ring typically show up once a week, but since we're getting awfully close to the Creators Update, it's beginning to happen more frequently. It's only been two days since build 15058 was released, but Microsoft today is offering Windows 10 for PCs build 15060 to the Fast ring.
Just like the one we saw earlier this week, there is no Windows 10 Mobile counterpart to go along with it. The latest build for phones is 15055, and the current Slow ring build is 15051, both of which have a known issue that involves background tasks not running. This is something that the company would want to fix prior to the RTM.
But since we're so close to general availability of the update - which should be next month - there's quite a bit of speculation around the RTM build. Microsoft is reportedly finalizing it this week, so it doesn't seem likely that this is the final build - especially since there's no Windows 10 Mobile build - but next week seems like a possible target.
The company has already said that PC users will get the Creators Update first, but that should generally be speaking about the Production ring. Insiders should get the RTM build at the same time across all platforms.
It's also worth noting that the build numbers will be aligned when the final versions are available, meaning that they'll be the same across PCs, phones, Xbox, HoloLens, and any other device that Windows 10 runs on. It's the same story as when 14393 was the build number for the Anniversary Update, and it was 10586 for the November Update.
Naturally, there are no new features in today's build; instead, it focuses on fixes. Once Microsoft signs off on an RTM, it will be promoted to the Slow ring, and later to Release Preview. Between now and general availability, there will likely be a couple cumulative updates as well.