Pro-Formance Advantage: Hardballs
Baseballs may look the same on the outside, but interior components and the cover material can differ greatly, having an impact on your performance.
Specific balls are made for different age groups and divisions. In Canada, most players are taught using a flat seam ball, allowing them to learn how to throw different pitches without relying on the seams for grip. As they advance through the divisions, raised seams will enhance their pitching ability and technique.
Pro level balls use a high-grade leather, hand sewn stitches, smooth seams, cushion cork centres surrounded by rubber, and a high percentage of natural wool batting for impact absorption. The more wool and rubber that protects the cork center, the better the durability and performance of the ball.
Composite centres are a blend of rubber and cork, and usually use less natural wool and more synthetic materials. These are good for Pee Wee levels and below.
Balls that have an oversized cork centre with no rubber sheath and a thin layer of wool are good for kids and recreational players. These are softer and are intended for weaker hitters.
For indoor training and T-ball players, a softer ball with a synthetic cover with flat seams that has a reduced injury factor (RIF) offers safety and durability.
Source For Sports® baseball experts will help you determine the right hardball for your age, division, league and ability.