At a time when Microsoft is expected to release the Windows 10 Mobile OTA update at the end of this month, A set of smartphones that will be upgraded to Windows 10 Mobile have been revealed.

The Lumia 950, Lumia 950 XL, Lumia 550 and the all new Lumia 650 are the only smartphones that come with Windows 10 Mobile preloaded. Other Lumia devices are either running on Windows Phone 8.1 or preview version of Windows 10 Mobile. The Redmond giant is expected to release the Windows 10 Mobile upgrade by Feb. 29.

Except for some unsupported Lumia devices, all the other smartphones that are running on Windows Phone 8.1 and Lumia Denim are eligible to receive the Windows 10 Mobile upgrade. When Microsoft will begin the roll out the upgrade, all the devices won’t be able to receive the upgrade at the same time.

According to Mobi Picker, the first set of smartphones that will be receiving the upgrade include: Lumia 930, Lumia 830, Lumia 735, Lumia 640, Lumia 640 XL, Lumia 634 with 1 GB of RAM, Lumia 540, Lumia 535, Lumia 532, Lumia 435 and Lumia 430.

The Redmond giant had announced at the middle of last year that it would be releasing Windows 10 Mobile upgrade for eligible devices by December 2015. However, the company could not keep its promise and it again announced that the update would arrive early next year. The update did not arrive in January and its arrival was further delayed until February.

Even though an employee from Microsoft Mexico has mentioned on Facebook that the software upgrade would be available by Feb. 29, there has been no official confirmation on it from Microsoft. It is the same source that had revealed the details of the Lumia 950 and 950 XL smartphones two weeks before their release.