Tennis balls originally were made only of rubber. This was improved when the balls were covered with flannel that was stitched around the rubber. The original color was black or white. Yellow balls were accepted to the standard by the International Tennis Federation in 1972, which allowed only one standard ball. In 1989 high altitude balls were incorporated into the rules. Today, the rules allow four types of balls: fast, medium, slow and high altitude.
Color and Material
All tennis balls are required to have a uniform outer surface with a fabric cover. These days, the color needs to be white or yellow. Any seams must be stitchless, according to ITF.
Weight
Weight for all tennis balls needs to be 1.975 to 2.095 oz. Regulation size is 2.575 to 2.7 inches for fast, medium and high altitude balls, and 2.75 to 2.875 inches for slow balls, according to ITF.
Rebound
Balls need to conform to standards in a rebound test in which the ball is dropped from 100 inches. The ball needs to rebound to a height of 53 to 58 inches unless it is a high altitude ball. High altitude balls need to rebound to 48 to 53 inches. The measurement for the drop height and the rebound height are taken from the bottom of the ball to the surface it's dropped onto. Balls are changed during tournament play, reports BBC Sport, because they start to lose their bounce following about three hours.
Testing Conditions
The testing of tennis balls to ensure the meet regulations is done under certain climate conditions. Tests are done at a 68 degree F and a relative humidity of 60 percent. The atmospheric pressure needs to be 30 inches Hg. Balls are removed from containers and kept at these conditions for 24 hours prior to testing, according to IFT rules.
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