The Duo, which was unveiled in October, has two 5.6-inch touch screens that open and close like a small book. The device is compatible with Microsoft’s Surface Pen stylus for handwriting and the company’s Xbox game controller for video gaming.

Customers are supposed to receive their Duos on Sept. 10.

Microsoft chief product officer Panos Panay says the Duo is aimed at people looking for a new way to work on the go, on something that is between a tablet and a phone. “I’m not trying to reinvent the phone, but I do believe this is a better way to get things done, a better way to create, and a better way to connect on a mobile device,” he said during a virtual press conference earlier this week.

The preorder period starts as the mobile market is still trying to recover from the COVID-19 pandemic. Smartphone sales plummeted 25% in the second quarter. The Duo’s price tag will test whether many consumers are willing to spend big money on a phone during difficult economic times, particularly on a device that lacks the most hyped new feature of 2020: superfast 5G Internet connectivity. So far, consumer interest in rival folding phones like the Motorola Razr and Samsung Galaxy Fold has been tepid, at best.

The Duo marks Microsoft’s return to the smartphone market four years after it stopped making devices relying on technology acquired from Nokia and running its Windows mobile software. The Duo uses a version of Google’s Android phone software and includes access to Google’s Play store with its millions of mobile apps.

“When it comes to mobile apps, the answer is Android,” Panay explained. “I love what’s possible with Windows and everything we’re doing but Microsoft has to light up on every platform.”

Though Google and Microsoft compete in many areas, particularly cloud services, they collaborated on the Duo, extending the features of Android to let apps take advantage of the two separate screens. The technology they developed can be used by any app developer on any phone that features dual screens.

All of Microsoft’s mobile apps, including its Outlook email program and OneNote note-taking app, can take advantage of the Duo’s two screens. In Outlook, for example, the app can show a list of emails on one screen and the contents of a selected email on the other screen. Other major apps, including Spotify and Amazon’s Kindle e-reader, have also been updated to work with the Duo’s two screens.

When unfolded, the 5.6-inch screens are only 4.8 millimeters thick, a little more than half the thickness of an iPhone 11 Pro or Samsung’s Galaxy S20 5G. But when folded closed to fit in a pocket, the Duo is about 2 millimeters thicker than its rivals. The Duo weighs 250 grams, or nine ounces, more than the iPhone, at 188 grams, and the S20, at 163 grams.

The Duo has just one camera that can be used for taking pictures, snapping selfies, or making video calls. The camera, which has a resolution of 11 megapixels, can shoot 4K video at 30 frames per second. Photos were “not a primary focus” in designing the Duo, Panay admitted.

Consumers can preorder the Duo from Microsoft’s website or buy it from AT&T or Best Buy. Despite the sales exclusive, the phone will work on all three major U.S. wireless networks, including Verizon and T-Mobile, Microsoft said.