Gamma(r) Quick Kids(tm) foam balls are low-compression, low-bounce balls specifically designed for kids learning to play tennis. This foam ball is smaller, softer and has a lower bounce than the Revolution foam ball, making it easier for young kids to hit consistently. Quick Kids(tm) foam balls are designed specifically to conform to the USTA(r) QuickStart Tennis format (36/60) standards for foam teaching balls on a 36" court.