Lots to tell about it. Search for "mass bias" (MB) or "preffers spin axis" (PSA).
A ball has three RG values, which define the distribution of the weight inside of it. The lower the RG, the more center-heavy the weight is distributed.
Then, you have the RG differential. It is the difference between the highest and lowest RG value created through the core. It tells you about the flare potential of a ball, how far the track fan can be spread through the pin's placement which marks the top of the core and the top of the highest RG axis through the ball.
The intermediate differential measures the RG difference on an axis that is at 90° to the highest RG axis through the ball and measures how much of the weight inside of the ball is shifted to a certain "side". This "side" determines around which axis the core wants to roll once it rotates. Every ball has this rating, but in some cores this force has been exploited because you can use it to influence the ball's motion shape, how fast it actually migrates towards its stable end roll axis (which is called Preferred Spin Axis), and the "power" that is used is called mass bias, measured by the intermediate differential.
It can be created through asymmetrical cores, but also through different weight distributions like different material densities. Numbers are better to judge what you actually have at hand (and I think the KP has only a low MB rating).
Normally, only balls with a significant mass bias have it marked on a ball (with an extra pin which has to be 6.75" away from the pin, exact at 90° to it), but sometimes it is also marked for marketing purposes (Hammer did it some time ago with a "LMB" engraving. One can argue at which value the influence of the MB is/becomes significant. IMHO it starts at about 0.015" (and today we have ball that exceed the 0.03" rating!), and it calls for slightly different drilling techniques and an experienced ball driller who knows your game, the ball and what to make of both.
A high MB does not make a ball "better" - it offers the driller extra option for recation tuning, and such balls are IMO good choices when you have a stable game, and when you know very well what you want out of a ball. From my experience, strong MB balls are more limited in use, less forgiving, but when they can be used on the conditions they were set up for, they truly offer an extra punch.
Hope this helps as a rough, others might correct mistakes or add some explanations.
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DizzyFugu - Reporting from Germany
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