Cue sports playing nine-ball. Snooker balls are smaller than American-style pool balls with a diameter of 52.5 mm ( in), and come in sets of 22 (15 reds, 6 "", and a cue ball). English billiard balls are the same size as snooker balls and come in sets of three balls (two cue balls and a red, an object ball). Other games, such as bumper pool, have custom ball sets. Billiard balls have been made from many different materials since the start of the game, including clay, bakelite, celluloid, crystallite, ivory, plastic, steel and wood. The dominant material from 1627 until the
Six-red snooker feature shorter frames, due to fewer red balls. Other formats are being considered as well. It was hoped that the format would revive the popularity of snooker as a spectator sport, in the same way Twenty20 has done to cricket. Jimmy White said that six-red snooker could be one way of helping boost the game's popularity. Ali Carter also said he would be interested in playing the format. The first international tournament in this format was contested in July 2008, with Ricky Walden defeating Stuart Bingham in the final. A six-red tournament was held during the 2009 World Snooker Championship