A tennis ball is a ball designed for the sport of tennis, approximately 6.7 cm (2.7 in.) in diameter and is normally yellow in color. In the early days of tennis, balls were often made of leather stuffed with hair or wool. Early tennis balls were made by Scottish craftsmen. These tennis balls were commonly made from a wool-wrapped stomach of a sheep or goat and tied with rope. In the 18th century, ¾” strips of wool were wound tightly around a nucleus made by rolling a number of strips into a little ball. String was then tied in many directions around the ball and a white cloth covering sewn around the ball. This type of ball, but with a rubber core, is still used for the original game of tennis, today called real tennis. With the introduction of lawn tennis in the 1870s, vulcanized rubber was first used to manufacture balls, often in tubes of four with a package, but not with the name of the brand.

Modern balls are made from rubber mixed with 14 to 18 chemicals to get the proper consistency. Approximately 85% of the ball weight is the rubber/chemical mix. The most expensive ingredient in the ball is the felt, which is adjusted in various ways to produce different properties. Steaming the felt raises its nap to make it fluffier, which increases wind resistance and control while reducing bounce and speed.

Pressure-less balls usually have a stiffer, woodier feel than pressurized balls, and except for the Tretorn brand, do not bounce as high as brand new pressurized balls. Unlike pressurized balls, though, they do not lose bounce over time. In fact, they get bouncier as they get lighter, due to fuzz loss.
Tennis balls must conform to certain criteria for size, weight, deformation, and bounce criteria 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 inches). Balls must weigh between 56.0g and 59.4g (1.975-2.095 ounces). Yellow and white are the only colors approved by the United States Tennis Association (USTA) and ITF, and most balls produced are fluorescent yellow (known as “optic yellow”) the color first being introduced in 1972 following research demonstrating they were more visible on television.

By using slower balls the starter players have more time and more control to make the game more fun for them at the introductory stage. The ITF Intro to Tennis Task Force recommends the red, orange, green progression for starter players. Using these slower balls will help the players to develop the most efficient technique and to be able to implement tactical situations in matches that, in most cases, could not be performed using the normal ball on a full court.