The Yonex Muscle Power 30 orange tennis balls are dedicated for stage 2 of the Play+Stay program and usable on 3/4 courts for young players developing their skills and earning their place in the world of tennis. The ball is 50% slower to ensure an easier learning curve, better control over the ball and subsequently an excellent precision practice. The balls are shipped in a bucket which contains 60 balls, and there are approved by the International Tennis Federation.