Modern billiard balls are made from "phenolic resin", which is a type of very strong plastic. The size of carom billiards balls is normally 61.5 mm (2⁄ in) in diameter. They weigh between 205 and 220 grams (7.23 – 7.75 ounces; 7.5 is average), and are quite a bit larger and heavier than the balls used for pool games. While UMB, the International Olympic Committee-recognized world carom billiards authority, permits balls as small as 61.0 mm (approximately 2⁄), no major manufacturer produces such balls any longer, and the main standard is 61.5 mm. The three standard balls in most carom billiards games are a completely white cue ball, a second cue ball sometimes having a red or black dot on it (to help people in telling the balls apart), and a third, red ball. In some sets of balls, however, the second cue ball is solid yellow. Both types of ball sets are allowed in tournament play.