The unique, very fine, open-cell structure used in the foam rubber makes them extremely difficult to tear and pick apart. Balls will withstand rough use and keep on playing. Ideal for training and instruction, volleyball, soccer and more. They can be hit, thrown, bounced-indoors and out- and are stingless. They're so tough, we put our unconditional 2-YEAR NORMAL-USE GUARANTEE on each ball. Tennis size. SIZE: 2 3/4'' dia.