I have only used it on a laptop....
(laptop only has 1 plug...)
and this will let you plug in keyboard and mouse...
but I have not plugged it into a desktop before...
This one is slightly different. I tried the mouse/keyboard one, and it won't work on a desktop. This one is for two keyboards.
However, all the other dual keyboard adapters I have seen need some kind of microcontroller and I don't think this has one. I suspect the LED's may not function correctly with this one, but if someone has used it and can verify that it works fine, I would be very interested in it.