International book international book of favorite sports_FV | Page 131

rubber with a felt coating. Traditionally white, the predominant colour was
gradually changed to optic yellow in the latter part of the 20th century to allow
for improved visibility. Tennis balls must conform to certain criteria for size,
weight, deformation, and bounce to be approved for regulation play. The
International Tennis Federation (ITF) defines the official diameter as 65.41–
68.58 mm (2.575–2.700 in). Balls must weigh between 56.0 and 59.4 g (1.98 and
2.10 oz). Tennis balls were traditionally manufactured in the United
States and Europe. Although the process of producing the balls has remained
virtually unchanged for the past 100 years, the majority of manufacturing now
takes place in the Far East. The relocation is due to cheaper labour costs and
materials in the region.
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