Tennis balls are inflated, felt-covered rubber balls of approximately 2.7 inches diameter. The usual color of a tennis ball is yellow, although it may give the impression of being green due to its fluorescent nature.

History of Evolution of Tennis Balls

Earlier,tennis balls were made of a variety of material, such as:

• Leather and stuffed with hair or wool
• Stomach of a sheep or goat, wrapped with wool and tied with a rope
• Animal fur
• Pine wood
• Rope made from the intestines and muscles of animals

However, the modern tennis ball seems to have directly stemmed from those made in the 18^th century. Strips of wool (3/4 inches in length) were tightly wound around a nucleus made of cork. Then a string was tied around that ball, after which the entire thing was covered and sewn with a white cloth. Tennis balls with a cork core and a cloth covering is still used in the original game of tennis, now known as, Real Tennis.

Modern tennis balls are made from vulcanized rubber (rubber cured with sulfur), a compound that is highly durable and strong, with the right consistency. The most expensive ingredient in a tennis ball is felt, which can be adjusted in different ways to alter of the ball's properties. Steaming the felt heightens the nap and makes the substance fluffier. This increases the ball's wind resistance and control, while reducing the bounce and speed. A compact nap causes a tennis ball to skip on striking the racket or hitting the ground.

Types of Tennis Balls

The two main type of tennis balls are:

• Pressurized - Such balls have a hollow core, filled with nitrogen. The pressure lasts for approximately a month, after which the ball becomes 'dead'.
• Pressureless - This type of tennis ball has a solid core and is suitable for those training themselves in the game. The ball does not lose its bounce easily. However, there are chances of the felt wearing off soon.

Some other kinds of tennis balls are:

• Regular duty tennis balls - These are meant for use in indoor and clay courts.
• Extra duty tennis balls - These must be used on grass and concrete tennis courts. If used on clay, the ball might get too fuzzy.
• High altitude tennis balls - These are used in high altitude regions, such as Denver, where the land is 4000 feet or more above the sea level. Regular balls have greater bounce at elevated levels.