If your game is slow pitch softball, then your ball is the Thunder ZN Polycore Softball. Deliver your best game with the best ball in softball construction. 12" Non-Association Slowpitch Softball Center: Poly Precision blended cross-linked polyurethane system High density and maximum resiliency Ultra-thin ZN composite cover to get to the core faster Seams: Flat COR: 0.44 Compression: 375 lbs.