Tennis balls are small, round objects used in the sport of tennis. They are typically made of a rubber core covered with a layer of felt, which helps them bounce and provides grip. Standard tennis balls are bright yellow, making them easy to see during play. The size of a tennis ball is about 2.57 inches in diameter, and they weigh around 2 ounces. They are designed to be durable and maintain their bounce over time. Tennis balls are used in various formats of the game, including singles and doubles matches, and are essential for both recreational and professional play.