The description says this has an internal rechargeable battery, but one of the pictures shows it takes 2 AAA batteries (not included). Which is it? Or is it both?

The product has a built-in rechargeable battery and does not require the use of AAA batteries.

Questions & Answers: Bailink Rechargeable Ergonomic Mouse, Vertical Wireless Mouse - Rechargeable 2.4GHz Optical Vertical Mice : 3 Adjustable DPI 800/1200/1600 Levels 6 Buttons, for Laptop, PC, Computer, Desktop, Notebook

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Bailink Rechargeable Ergonomic Mouse, Vertical Wireless Mouse - Rechargeable 2.4GHz Optical Vertical Mice : 3 Adjustable DPI 800/1200/1600 Levels 6 Buttons, for Laptop, PC, Computer, Desktop, Notebook

ERGONOMIC, SLEEK AND RECHARGEABLE DESIGN -- Scientific ergonomic design encourages healthy neutral "handshake" wrist and arm positions for smoother movement and less overall strain
MULTIFUNCTION AND CONVENIENT -- Advanced "Page Back" and "Page Forward" functionality buttons provide convenience when web page browsing. 800 /1200/1600 DPI Levels -- Easily adjusts the sensitivity of the mouse
HIGH-CAPACITY RECHARGEABLE BATTERY -- Built-in rechargeable battery. You no longer need to buy batteries, very convenient !! EASY TO USE -- One nano USB receiver at the bottom of the mouse, Just Plug and Play!
WIDELY COMPATIBLE -- Widely compatible with Windows 2000 / XP / Vista / 7 / 8 / 10 / Linux. Note: Not compatible with Mac OS, Apple Products Once you get used to the ergonomic mouse, you will love it so much !

$22^.99 –