The Dunlop Stage 1 green mini tennis balls are great for coaching and training and have the International Tennis Federation approval. They are approximately 25% slower than a standard tennis ball to give you more confidence and time to prepare your return shot. The balls are designed for children aged 9-10 and they are perfect as transition balls from Stage 2 to standard tennis balls. The mini tennis balls are supplied in a pack of 1 dozen (4 tubes of 3 balls).