Cover Stock - Bowling balls are made of four main different types of Coverstocks-Plastic, Urethane, Reactive Resin, and Particle (Proactive).
Core Type - There are two types of bowling-ball cores. A symmetrical core is the same all the way around one axis, although it is not necessarily the same around another. That is, it may be symmetrical horizontally, but not vertically. In that case, though, there is a marking on the bowling ball (called the pin) that denotes where the center of that symmetry is. This lets your ball driller know how to properly layout the ball and take advantage of the symmetry.
Asymmetrical cores have a greater distribution of weight in one spot than another. Often, these balls work well for bowlers who struggle with putting a significant number of revolutions on their shots, as well as in specific situations for high-level bowlers.
Radius of Gyration - High RG numbers indicate that the ball's mass is distributed more towards the cover (cover heavy) which promotes length through the front end of the bowling lane. Low RG numbers indicate that the balls mass is distributed more towards the center (center heavy) which promotes an earlier roll through the front part of the lane. Medium RG describes sufficient bowling ball skid length to reach the mid-lane before transitioning into the hook phase of overall motion.
Total Differential - Differential of RG is described as a measurement varying numerically from .01 - .08 in range. These measurements describe the bowling ball flare potential rating and indicate if the flare potential is low, medium, or high. The higher the number, the greater the track flare potential and the more angular motion the ball will produce from the break point to the pocket. The lower the flare potential, the ball will yield more of a smooth arc motion on the back end of the lane.
Intermediate Differential - Int. Diff determines the strength of the PSA. The stronger the Int. Diff the faster the spin time of the PSA. The faster the spin time of the PSA the shorter the hook zone on the lane. Which means the ball will transition from Skid-Hook-Roll faster.
Torque - Rev Rate