Amazon.com: Logitech 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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Wireless Dongle Receiver Unifying USB Adapter for logitech Mouse Keyboard Connect 6 Device for MX M905 M510 Keyboard K400 - AliExpress
Logitech Unifying Receiver for Connecting Multiple Devices