Just in case you didn't notice,I really love quack products. I've taken apart similar units to this in a plug-in version, but this is a stand-alone aluminium case version.
OK, it's smaller than I was expecting, but that's just one of those things. It uses pretty much the same circuitry, basically a capacitor in parallel with the mains, but has a more sensible LED drive circuit and a fuse too.
These things claim to lower your electricity bill by filtering/improving the mains sinewave. They're loosely based on power factor correction, but as that has no effect on a home electricity meter they won't show an effect. They are also just a random capacitor value permanently applied across the mains, whereas proper power factor correction should be matched to a specific load.
This version is quite stylish.

This video also shows how accurate the capacitive reactance formula is.

If you enjoy the channel you can help support it with a dollar for coffee, cookies and quack overunity devices at   / bigclive