This is just a stabilizer (dampener). It’s pretty much what is typically used in archery. They work very well when mounted to a bow which has a very low and strong frequency resonance/oscillation when "fired".
In a standard design the dampener basically is the combination of a dampening material and a dampening weight. On a cue stick the dampener would be mounted to the end of the cue, and the dampening weight would “effectively” be on the other side of the dampening material (in reality the weight could be mounted in a few different ways actually, that’s why I say effectively).
Mounting the dampener will have two effects on a cue stick, the most noticeable but least important being that it will add weight to the back of the stick. The other more important effect (and the purpose of the dampener) being that it will reduce some vibration that travels to the back of the cue and then subsequently reducing any secondary vibration “reflected” back up the shaft and reducing secondary vibration transmitted into the shooters hand and/or back to the tip.
In reality, a proper stabilizer would need a few design considerations specific to a cue application (just a few points):
-The weight must be weighted for the weight of the cue
-The axis of movement for the weight must orientated to the directionality the properties of both the cue sticks vibration and the dampening material vibration.
-The dampening material needs to have the correct properties (elasticity, density, etc…) to affect the desired frequency range needed to dampen the desired vibration. If the wrong material is chosen it could only provide minimal dampening, or possibly even make things worse.
The point of the above is to highlight that if a dampener for say an archery bow is just pulled off the shelf and redesigned to mount on the end of a cue stick… I’m not confident that will be so effective and useful, and it could actually make things worse even if it feels like the cue plays better. If on the other hand a dampener was designed to operation for the same dynamics as a pool cue… Well that might work, for those seek the small improvement it would add and don’t care about the change in weight balance.
In the end, I say if you feel like it makes a difference, or if you just plain like it and damned the science, then just go for it… Even if it might be just a gimmick. Just don’t ever convince yourself that it will fix your game or that you need it to win… And heaven help you when you have to play with just a house cue on beer night with your buddies.
Earl plays with wraps, weights, heck I wouldn’t be surprised if he whipped out fuzzy ear-muffs someday… If that helps him achieve his goal, more power to him.
That’s all just my unscientific opinion, and as always your mileage may vary. Sorry for the long post.