One of the features most eagerly awaited by Windows 10 users is extensions support for Edge. On March 17, those users -- at least the ones on the Fast Ring Insider test builds -- are getting a preview of what to expect on this front.

Windows 10 "Redstone" build 14291 is available for PCs and phones for download today, incorporates an early look at extensions for Edge, Microsoft's new Windows 10 browser.

Originally, Microsoft had been striving to make extensions part of Edge before the end of calendar 2015. But the team didn't hit that goal. Now Edge is expected to be part of the first Redstone Windows 10 release, which is expected to be made generally available around June 2016.

Information about Microsoft's Edge preview messaging leaked a couple of times in recent months: First in December 2015, and then again (in a modified form), earlier this week.

The first extensions available to testers are the ones that we heard about from the information leak earlier this week: Microsoft Translator, Reddit Enhancement Suite and Mouse Gestures.The Translator extension description says it will "translate foreign language pages for 50+ languages." The Reddit one is a "suite of modules" for enhancing Reddit, and the Mouse Gestures extension will "allow customers to perform basic browsing tasks by right-clicking and then gesturing with the mouse."

"Later this year customers will find popular extensions from partners like AdBlock, Adblock Plus, Amazon, LastPass, Evernote and more," according to today's blog post.

Once Microsoft releases Redstone 1 to customers, extensions will be available in the unified Windows Store. For now, testers need to download each extension directly.

There's also a new preview of the Windows Maps app available to testers today. The ability to pin tabs in Edge is new to Build 14291. The promised, combined Insider Hub plus Feedback App -- known as Feedback Hub -- is part of today's builds, as well.

The full list of what's new, plus known fixes and bugs, is in the Microsoft post about Build 14291.

As a reminder, Microsoft is cutting back which Windows Phones will be eligible for the upcoming Redstone preview builds. Existing Windows Phones not on that list are not going to get Redstone, but instead will work with "Threshold 2," the version of Windows 10 Mobile Microsoft initially released last Fall, plus any updates made to that release.