Review on 🔌 Logitech USB Unifying Receiver, Wireless Technology at 2.4 GHz, USB Plug Compatible with all Logitech Unifying Devices such as Wireless Mouse and Keyboard, for PC/Mac/Laptop - Black by Mitch Emmel

If like me you've lost your Unifying receiver, this is the right replacement. Although it is a bit smaller than its predecessor, it works just as reliably. Bought as a replacement for the K400 Plus Unifying receiver. DO NOT buy the C-U0007 Unifying receiver like me. The number of 1-star reviews should be a warning sign. I think I left my comments in the review as well, but at least on the K400 Plus, even though they were paired, the range is much worse than before. The C-U0007 basically required DIRECT line of sight and would drop inputs if something was blocking it like a tabletop or even if it was further than 6ft. Save yourself the hassle and just do it. Either way, it's likely an updated design.