Yes, that is a Mi Band 5 display on the back of Mi 11 Ultra Xiaomi Mi 11 Ultra

The Xiaomi Mi 11 Ultra and the Mi smart band 5 have a feature in common. Xiaomi’s top of the line flagship phone in the Mi 11 series, the Mi 11 Ultra was unveiled a couple of weeks back in China with a few exciting features and one of them is the fact that the phone comes with a tiny secondary display on the back. 

Xiaomi’s CEO, Lei Jun in his live video on Chinese social media platform revealed that the display which sits next to the camera module on the rear is from Mi Band 5. The Mi Band 5 sports a 1.1-inches 126 x 294 resolution AMOLED display with 450 nits brightness.

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Xiaomi Mi Smart Band 5

(Image credit: Mike Sawh)
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Xiaomi Mi Smart Band 5

(Image credit: Mike Sawh)
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Xiaomi Mi Smart Band 5

(Image credit: Mike Sawh)