Vibration Dampeners

What does it do?
The main purpose of the dampener is to help minimise the vibration that is caused when the ball hits the strings of the tennis racquet.

Do I need one?
This is a very personal decision, some players swear that these small rubber devices help them with the prevention of Tennis Elbow, but this is not scientifically proven.

Where do I place the Vibration Dampener?
In lines with the ITF rules of tennis, the dampener can be used, "but these devices may only be placed outside the pattern of the crossed strings." 

So they can be placed left, right, top or bottom of the string pattern. The most common area is the bottom of the string pattern. It is usually placed in the middle of the two centremost vertical strings and just below the first cross string.