Tennis balls
Requirements
The International Tennis Federation (ITF) dictates the following for tennis balls:
  • the outer shell of the ball must be uniform and seamless
  • the ball must be yellow or white
  • the ball must have a mass of more than 56 g and less than 59.4 g
  • the ball must have a diameter of more than 6,541 cm and less than 7,303 cm
  • the ball must be yellow or white
  • each ball must have a jump height of more than 135 cm and less than 147 cm when it is placed from a height of 254 cm on a flat, hard surface, eg. as if concrete is dropped
The felt around the tennis ball is a superficial sheath that protects the underlying rubber ball from abrasion. In addition, the felt improves the flying and jumping properties of the tennis ball. The more a ball is played, the lower the pressure in the ball and the slower it gets.
Types of tennis balls
Internal pressure balls
Internal pressure balls are made by filling the felt covered rubber bubble under overpressure. The tennis balls are not 100% air-tight, so they are stored in an airtight box. In the can, the same pressure prevails inside the ball. Internal pressure balls are mainly played in competitions and tournaments, as they offer a good feeling. Due to their relatively short lifespan they are regularly replaced in the match.
Non-pressure balls
Non-pressure balls are made by assembling the two halves of the rubber covered by the felt, without consideration of air pressure, etc. The pressure inside the ball corresponds to the ambient conditions. Therefore, unpressurized balls need not be specially packaged. The jumping properties of this ball are determined solely by the rubber composition. With unpressurized balls, the jump and play characteristics are retained much longer, since no pressure can be lost. They should be replaced when the core hardens or the felt is worn. Their longevity makes them ideal for tennis training.
Tennis balls for children
There are special tennis balls for kids that are 25%, 50% and 75% pressure reduced. More information can be found in the „Kids World“.