Billiard Congress of America – World Pool-Billiard Association publishes rules for American-style pool games such as Nine Ball, Eight Ball, Ten Ball, Black Ball and Continuous Pool. The specifications for the balls seem to be consistent among all the games, as long as you play by the American-style rules.
16. Balls and Ball Rack
All balls must be composed of cast phenolic resin plastic and measure 2 ¼ (+.005) inches [5.715 cm (+ .127 mm)] in diameter and weigh 5 ½ to 6 oz [156 to 170 gms]. Balls should be unpolished, and should also not be waxed. Balls should be cleaned with a towel or cloth free of dirt and dust, and may also be washed with soap and water. Balls contaminated with any slippery substance – treated with a polishing or rubbing compound and/or waxed – must be cleansed and dewaxed with a clean cloth moistened with diluted alcohol before play.
A complete set of pool balls consists of one white cue ball and fifteen color-coded, numbered object balls. The object balls are clearly and highly visibly numbered 1 through 15. Each object ball has its number printed twice, opposite each other, one of the two numbers upside down, black on a white round background. The object balls numbered 1 through 8 have solid colors as follows: 1=yellow, 2=blue, 3=red, 4=purple, 5=orange, 6=green, 7=maroon and 8=black. The object balls numbered 9 through 15 are white with a centered band of color as follows: 9=yellow, 10=blue, 11=red, 12=purple, 13=orange, 14=green and 15=maroon. The two printed numbers 6 and 9 are underscored.
The wooden triangular ball rack is the recommended device to be used to rack the balls to ensure that the balls are properly aligned and in contact with each other. Both surfaces that can make contact with the table-cloth when moving loaded rack to and fro, should be very smooth in order not to incur any damage to the cloth underneath. Plastic racks are not recommended, they are flexible and tend to deform, making proper racking of balls time-consuming, if not impossible.
Billiard Congress of America – bca-pool.com
Photo – commons.wikimedia.org/wiki/File:Billiards_and_snookers.jpg