Category: The tennis training balls are suitable for both adults and children for training purposes Material: Made from rubber and felt materials, these tennis balls are designed to withstand heavy use Size: Each ball has an approximate diameter of 6.4 cm/2.52 inch, making it the proper size for training sessions. Elasticity: With an elasticity range of 1.1 from to 1.15 m, these tennis balls provide a good flexibility that enhances your training experience Packaging & Storage: The set includes 20 tennis balls packed in a drawstring bag for easy storage and transportation Specification: Material: Rubber Felt Size Chart: Diameter: 6.4 cm/2.52 inch Package Includes: 20 Tennis Balls Note: Please allow slightly errors 1-2cm differences due to manual measurement.