Red Ball 1 Ages 4-10 years old. 10 and Under Tennis: An exciting new approach to introduce kids to the game. Balls are lower in compression meaning they bounce lower and slower so they are easier to hit. This allows kids more time to get to the ball and helps them develop proper swing patterns. The racquets are smaller, lighter, and sized for smaller hands. The courts are smaller and easier to cover and scoring is modified to allow for shorter matches. This all adds up to more success and more fun. Red Ball: A red ball has the least compression of the 10 and Under balls and is 75% slower than a regular tennis ball. It has the least bounce, moves the slowest through the air, and travels the least distance making it the ideal ball for beginning 10 and Under players.