Original: While UMB, the International Olympic Committee-recognized world carom billiards authority, permits balls as small as 61.0 mm (approximately 23 â 8), no major manufacturer produces such balls any longer, and the de facto standard is 61.5 mm.
Simplified: While UMB, the International Olympic Committee-recognized world carom billiards authority, permits balls as small as 61.0 mm (approximately 23 â 8), no major manufacturer produces such balls any longer, and the main standard is 61.5 mm.