The most adaptable tennis ball ever designed for any player, any surface, and any time of play is the Wilson Championship Tennis Ball. These tennis balls include a special Dura-Weave felt that offers incredible resilience and holds up even at high altitudes. The ITF has examined and endorsed these tennis balls. a ball that may be used by any player at any moment and is versatile. Unique wool felt mixture that enables significant durability improvements. The core substance, last but not least, enables excellent playability and consistency.