In the clearest sign yet that Windows 10 version 1803 is complete, Microsoft has delivered the final build to the Windows Insider Slow Ring.

As Mehedi reported just days earlier, Microsoft released Windows 10 build 17133 to Insiders in the Fast ring on March 27. This is the final build of what’s called, variously, Windows 10 version 1803, Windows 10 “Redstone 4,” and the Spring Creators Update.

So, yes, its names are legion. But so, too, are the various milestones through which this build must pass on its way to RTM (Release to Manufacturing). The release to the Fast ring is the first external milestone. And the subsequent release to the Slow ring is the second.

This milestone is doubly important, however, and for two reasons.

First, when a build does makes its way to the Slow ring, that release usually trails the Fast ring release by a week. This time, the delta was just 3 days, suggesting that the quality is where Microsoft wanted it. Plus, that March is coming to a close and its internal schedule for this release dictates a March completion.

Second, this means that the “magic window” I described a few days back is now available to everyone testing Redstone 4. If you wish to get your enrolled PCs off the Insider train and back on to the normal, public release schedule, now is the time to do so. (I’ve done this to all of my own PCs.)

Well, almost all testers, I guess. Microsoft is once again doing unsolicited A/B testing on Insiders, so only some Slow ring users will actually see this build immediately.

The good news? This is super-temporary.

“We have released Windows 10 Insider Preview Build 17133 (RS4) to Windows Insiders in the Slow ring,” Microsoft’s Dona Sarkar announced yesterday. “As part of this [release], we are testing the engineering systems responsible for the deployment of Windows 10 feature updates to customers. As such, not all Insiders in the Slow ring will be immediately targeted to receive this flight. We are targeting full availability to the Slow ring on Monday [April 2].”

And here’s some even better news: You can circumvent this one easily. Just open Settings, navigate to Update & Security > Windows Update, and click “Check for updates.” You will get the final build of Windows 10 version 1803.

That’s all she wrote, folks. The next and final public milestone happens Tuesday, April 10. That’s when Windows 10 version 1803 starts heading out to the public.