This number explains how the mass is distributed in the ball, which will give you an idea of how the ball performs. That is, when will the ball start rotating?
RG Scales
Every ball will rate somewhere between 2.460 and 2.800, although many ball manufacturers have converted to a 1-10 scale to give consumers an easier frame of reference.
The Meaning of the Ratings
A ball with a high RG rating (close to 2.800 or 10, depending on which scale the manufacturer uses) will have a mass distributed toward the cover, which is often referred to as “cover-heavy.” This type of mass distribution will give your shots more length. That is, the ball will travel through the front part of the lane while saving energy so it can start rotating as it nears the pins. These balls are well suited for dry or medium lane conditions, when you don’t want the ball to hook too early.
Conversely, a ball with a low RG rating’s (close to 2.460 or 1) mass will be distributed toward the center, otherwise known as “center-heavy.” These balls are valuable on oily lane conditions, as they’ll begin rotating earlier, giving you more time to grab the lane and get the ball to the pocket.
If you were to use a ball with a low RG rating on a dry lane, you may have trouble with overhooking your shots.
If you were to use a ball with a high RG rating on a wet lane, you may have trouble getting the ball to hook enough. This is one reason so many bowlers, especially those who bowl in a number of different bowling centers, carry an arsenal of bowling balls, giving them options when needing to adapt to a given lane condition.