Shell:

900 Global uses a numerical shell rating system (S10-S90) to specify the strength of its shells. The lower the number (S10) the less aggressive the shell. The higher the number (S90) the more aggressive. By using this system, 900 Global makes it easier to know the differences between all of their shells.

By using this shell rating and knowing the different core specifications, bowlers will be able to select the 900 Global ball that best matches up to their game and the condition they are bowling on.

Understanding Core specifications:

The Radius of Gyration (Rg) is an indication of the resistance to rotating motion. This affects how easy the ball wants to rotate off the bowler’s hand. The higher the Rg the less rotation applied to the ball. Therefore, the ball will go longer down the lane before it wants to hook. A lower Rg will result in more rotation off the bowler’s hand. This will result in an earlier hook motion. USBC sets a minimum Rg specification of 2.40 and a maximum Rg spec of 2.80.

Differential Rg is the other important core measurement. This property determines the track flare potential. Is it equal to the difference between the highest Rg value about any axis in the ball and the lowest Rg value about a different axis. The maximum allowable differential Rg is 0.060 inches. A ball with a differential on .030 will flare about 3”, a differential Rg of .050 will flare about 5”, etc. The more differential Rg a ball has the more potential for track flare. The flare allows a dry surface on the ball to contact the lane which create more friction then an oily ball surface. Thus a ball with a higher differential Rg will flare more and hook earlier than a ball with less flare.

The shell rating system applies only to performance balls. Polyester shells are not rated.