Logitech K400 Plus did not come with a USB dongle? Wait!! It's hidden in the box!! | THINKBOX
Amazon.com: Logitech USB Unifying Receiver, 2.4 GHz Wireless Technology, USB Plug Compatible with all Logitech Unifying Devices like Wireless Mouse and Keyboard, PC / Mac / Laptop - Black : Electronics
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Amazon.com: Logitech USB Unifying Receiver, 2.4 GHz Wireless Technology, USB Plug Compatible with all Logitech Unifying Devices like Wireless Mouse and Keyboard, PC / Mac / Laptop - Black : Electronics
Logitech Unifying receiver - Wikipedia
Logitech Unifying Receiver for Connecting Multiple Devices
Genuine Logitech Unifying Mirco Dongle Receiver USB For keyboard K400r K400plus | eBay
Logitech K400 Plus Touchpad Wireless Keyboard Black - Usb Wireless Connectivity - On/off Power Switch - 2.40 Ghz Operating Frequency : Target
Logitech K400r Wireless Keyboard With Touchpad & USB Receiver Black Tested | eBay