Greatest Dowsing Rod Ever Fantastic Sound Tuning Ability

Great - there will be plenty of suckers who will fall for this.
Looks like something you guys might use in your dungeon. 
This guy just can’t help himself.

Need two for proper balanced operation.

Plus... then they can also be used as nunchucks.

WHAT! No RCA option? I like faux carbon fiber dangle thingies.
 Prohibited by law for carrying in public!
At least there are some measurements to back up claims, however I question the efficacy of the product when the change with and without may be deemed by some as significant statistically, but imo marginal at -120dB. To me that says that whatever is being done is minuscule and in the realm of inaudibility. Someone with more technical expertise than me might jump in here. 

Now, having said that, if they were presented to me free to try, I likely would. My guess is they would fail my Law of Efficacy. However, I have been surprised before by products or settings which had a greater influence than I expected. But, the discussion on the website and measurements are not sufficiently compelling to seek a trial. YMMV 

There seems to be little controversy over plugs for unused jacks on components, so my guess is these would function similarly. I doubt we would get someone to do measurements on a comparison of simple plugs to these devices, but that could be insightful. I don't think I  have seen measurements for such plugs, and my guess is they might match up with the measurements of these devices closely. 
Without trying the subject of the thread in your own system fir an extended test period one cannot really draw any conclusions based on appearance, application or theory of operation. And even if the results of tests in ones own system are negative or negligible those results cannot be generalized to apply to all systems. Some audiophiles are all thumbs. Can you believe it?! If you could generalize Test Results every skeptic in town would be disparaging Mpingo discs, Schumann frequency generators, directional power cords, Message Foils, purple pens, and a host of other audiophile toys. C’est la vie! 🤠