Prince(R) Stage 3 Tennis Balls have a reduced ball speed of 75% compared to a standard tennis ball. This aids in the development of young or beginner players to ensure proper swing technique. The stage 3 tennis balls come in a netted bag, as a set of 12 balls, and are 3 stages away from using a regular adult-sized Tennis ball. Youth Tennis Balls USTA Stage 3 Youth Transition Tennis Balls Reduced ball speed Rebound: 35-41 inches Additional Details Package includes 12 tennis balls and mesh bag Best suited for ages 8 and under