For most of the development cycle, the two main Insider rings—Fast and Slow—offer builds of the next version of Windows. However, there’s a short window within the development cycle where Microsoft offering the build. We’re in that window right now: the Fast and Slow rings are both now on build 17134. This build has been deemed the stable build and hence was released on Monday, before beginning its wider distribution next Tuesday.
If you opt out of the Slow and Fast rings , your system will simply pick up the regular stable Windows updates as they’re released each month. If you wait too long, however, you’ll soon receive a Redstone 5 build. From there, the only way to revert to a stable build will be either to roll back the installation entirely—which normally works—or reinstall from scratch. The Release Preview ring, in contrast, will continue to track stable Redstone 4 releases for the next five or so months, up until the point that Redstone 5 is ready for release.
When will the Slow and Fast rings see their first Redstone 5 build? We don’t know exactly, but Microsoft’s Dona Sarkar has tweeted that it will happen soon and that you should make the switch “today” if you’re not ready to experience the new and unstable development stream.
None of this applies if you’re on the limited “Skip Ahead” ring, as that’s already made the leap to Redstone 5. To switch that to a stable build, you’re either going to have to wait until October or do a clean reinstallation.