The Wilson A9031 softballs are high-quality fastpitch balls made of durable leather material. Each dozen set includes 12 balls with a compression hardness of 375, perfect for softball players looking for consistent performance. The machine-stitched construction and size of 12 inches make these balls ideal for competitive games and practices, providing players with the COR of 0.47 for optimal performance on the field. Trust the Wilson brand for quality and reliability in your softball equipment.