For young players starting the game and learning the art of spin, the GAMMA Quick Kids 36 Tennis Ballls feature a two-tone felt for easy instruction. The Quick Kids 36 balls are USTA approved for 10 and under tennis and ideal for ages 8 and under on a 36' court. These lightweight balls feature a low compression core making them 75% slower than a standard tennis ball and providing a lower bounce. USTA/ITF Stage 3 Specification. BENEFITS & FEATURES: 75% Slower Speed: Made with a low-compression core and lightweight outer layer, these tennis balls fly 75% slower than standard tennis balls, making it easier for beginners to practice rallies and experienced players to practice more advanced techniques Training Tennis Balls: Designed for younger players learning the game, these beginner tennis balls are a great choice for use when instructing children on the fundmentals of tennis Two-toned Surface: Designed 15% larger with a bright yellow and red felt surface, these tennis balls offer added visibility and are easy to identify from standard tennis balls. They also help players practice hitting and returning topspin and slice shots Made for 36' Courts: Designed for players beginning on 36' courts, the slower and lower bounce makes these practice tennis balls suitable for beginners or youth tournaments USTA/ITF Stage 3 Specifications: These low bounce tennis balls are rated as stage 3 balls by USTA/ITF for use in tournaments for youth 10 and under