Gamma Revolution Starter Balls are designed with beginners and accomplished players in mind. The oversized foam balls have a Magnacore that offers a bounce similar to a standard tennis ball, but makes for an easier target for beginners. Accomplished players use them for warming up. Revolution balls confrom to the USTA QuickStart Tennis format standard for Stage 3 balls on a 60-foot court. Ideal for ages 6 and under. Case of 60 balls. Colors: Yellow/Red