The GAMMA Quick Kids 36 Foam Ball is USTA Approved for 10 and Under Tennis. Ideal for ages 8 and under on a 36' court with the 10 and Under Tennis or Tennis 10's format. 75 percent slower speed than a standard tennis ball. The Quick Kids 46 Foam Ball bounces lower than the Revolution foam ball so it is ideal for very young children. Two ton surface helps to learn and practice spin. USTA/ITF Stage 3 specification.