A compact magnetic e-ink reading accessory made by the brand XTENK. It’s designed to attach to the back of a smartphone, likely using a MagSafe-style magnetic system.

The device looks like a small standalone e-ink reader / secondary display for reading text with lower eye strain and lower power consumption than a normal phone screen. It resembles a miniature e-reader that can magnetically stick to a phone.

Key features highlighted in the Chinese text:

• Magnetic attachment design (“磁吸设计”)
• 219 PPI display with software optimization for clearer text (“219PPI 软件优化 字体清晰”)
• Low-power chip
• 650mAh battery
• About 10 hours of continuous reading
• Up to 7 days standby/light reading
• Physical page-turn buttons (“物理翻页按键，闭眼也不会错” — “physical page-turn buttons, easy to use even without looking”)

The device shown appears to function like a compact e-ink display for reading notes, books, or text snippets while attached magnetically to a phone.

Visual details from the image

• The device is shown attached to the back of an iPhone-like phone.
• It has:
  • a black-and-white e-ink screen
  • physical side buttons
  • a compact handheld size
  • minimalist styling
• One image shows a text-reading interface.
• Another shows a simple menu UI with icons.