The GAMMA 60 (orange dot) Ball is USTA Approved for 10 and Under Tennis tournament play. Ideal for ages 10 and under on a 60' court with the 10 and Under Tennis or Tennis 10's format. 50 percent slower speed than a standard tennis ball. Numbered 1-3 for tournament play. USTA/ITF Stage 2 specification. The GAMMA 78 (green dot) Ball is USTA Approved for 10 and Under Tennis tournament play. Ideal for Ages 11+ and adult beginners on a 78' court with the 10 and Under Tennis or Tennis 10's format. 25 percent slower speed than a standard tennis ball. Numbered 1-3 for tournament play. Stage 1 specification.