This ball is made of a rubber core of a basketball and common felt of tennis ball, it's much thicker than a normally pet tennis ball. But 

BTW, please fill the ball as hard as possible.
Genuine 6.3/24 cm Diameter Tennis Ball, Super thick!
Use for signature or pet toy (My dog loves this type tennis ball very very much).
Color: as picture

Package:1 X Dog Tennis Ball Toy