I recently bought a used pool table and didn't get the pockets shimmed prior to it being completely put together. You can't tell what you need until it is finished and by then it is too late. Would have cost me for felt and recovering the entire table to get it shimmed. It is said that the corner pockets should be about 4 1/2 inches wide. About the width of two balls. Mine was two balls and then some. Since I play league and the pockets are very unforgiving at my pool hall I figure this would improve my game.
I have to say it has helped in improving my game. The tighter pockets force me to have to put the ball down the center or deep in the pockets so they won't pop out. In that aspect it has helped.
They don't stay stuck to the pockets. When I am playing there are always one or two that fall down constantly. I understand they can't stick like glue but they are always falling down and it is very annoying. As of yet I haven't had anyone else playing on the table at the same time. However when I do I am taking them down as it would be embarrassing for them to keep falling. Add to it that they are green not gray as the picture shows. My table is Olive green which the gray would have been a nice contrast. The standard green is not bad just not what was advertised. Also it seems they only make one size. If you don't have a nine (9) foot table they don't fit properly. I have an 8 1/2 foot table and they don't fit the side pockets at all. The corner shims are actually too short and don't go all they way out the tips of the pockets.
The price wasn't bad so if you need them for practice they are fine. Just don't expect it to be the answer as they are not.
I would not recommend this product to a friend.