If you have a distance of 1" or less between CG and pin, you have a pin-in ball. Anything beyond this makrs a pin-out ball. This means that the core is in a position out of the center of the ball, and through this mass distribution offers a stronger reaction when the thing rolls (just like amish_ashaman explained). Pin-out balls offer a wider variety of drilling reactions. Pin-in balls are good for smooth reactions and dryer lanes, pin-outs for strong reaction and generally more oil.
If you look for advice on tech, take a look at ebonite.com. They have a very comprehensive glossary. And there are very good entries on this website as well (sorry that I cannot give you a link).
Top weight is another weight excess which can be used/shifted to influence ball reaction. The more you have, the bigger this influence might be.
Ask a local pro to help you with your ball choice. The ball and its weight distribution can fit very well to your local needs and the ball reaction you desire.
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DizzyFugu --- Reporting from Germany
"All that we see or seem, is but a dream within a dream..." - Edgar Allen Poe
Edited on 1/14/2005 2:45 AM