Last week following Microsoft's Build 2018 developer conference, the company released Windows 10 SDK Preview build 17666. It was the first SDK to target builds from the Redstone 5 development branch, including various features that were announced at the conference.
Today, Microsoft released SDK Preview build 17672, once again aligning the build number with the latest Windows 10 Insider Preview in the Fast ring.
Also, the firm hasn't published a blog post yet to announce the new SDK, although it will probably do so later today. This is not uncommon when it comes to new SDK Preview builds, so if you're interested in seeing what's new, stay tuned later on.
At this point, all builds that are currently in Redstone 5 preview should be on build 17672, except for Server, which is still on 17666. That means that alongside of the client build in the Fast ring and the SDK, there are images available for Desktop App Converter base images, Windows 10 IoT Core, ADK, WDK, and HLK.
If you want to download the new SDK Preview, you can find it here. If you want to download any of the other items mentioned, use the links on the right side of the page.