It was a good tool when 9ball was racked with the 1 on the spot and players where going for a square hit on the 1ball to get the wing ball in the corner and the 1 ball towards the side pocket AND controlling the CB to stay at the center of the table, using a stop hit that if done correctly, it will cause the CB to jump up off the 1ball and land in the center of the table.
This tool doesn't help at all with modern 9ball with the 9 on the spot, breaking from the box as players are focusing on making the 1ball in the side and sending the CB to the long rail and back to the center of the table (sometimes resulting in hitting and pocketing the 9ball).
You have to see that the 1ball goes into the pocket!! and adjust accordingly if you miss the pocket above or bellow it.
It will also not help if you are practicing such a break while also going to make sure that the 3 point rule is in affect.
Modern 9ball break is less about the CB control and more about the object balls control, so this tool will not be good for it. I don't care how much the inventor wants you to believe otherwise. trying to smear my (nick)name won't help with that either...
Pros that got it and used it, did it before the changes of the break in 9ball.
This tool will still provide good aid for breaks practicing if you are still going for a square hit and controlling the CB to stay at the center.
Like if the box is not in use and players can break from the side, they'll still go for the old style square break even if the 9ball is on the spot, you'll still get a ball at the top corner and the 1ball will go off the long rail towards the bottom corner.
It will also work to practice 8ball breaks unless you're looking for a second ball break, then again, it's useless.
10 ball breaks usually are hitting the top ball square so it'll work for practicing that, but who plays 10ball?
If I was an active trainer, I might have gotten such a device to work on the break with beginner students.
As a player in training, I would not waste money on such a device as it will become useless to the player progression very fast, as advanced players need to see where the object balls are going.