While UMB , the International Olympic Committee-recognized world carom billiards authority , technically permits balls as small as 61 mm ( 2.4 in ) , no major manufacturer produces such balls any longer , and the de facto standard is 61.5 mm ( 2.42 in ) .
While UMB , the International Olympic Committee-recognized world carom billiards authority , permits balls as small as 61.0 mm ( approximately 23⁄8 ) , no major manufacturer produces such balls any longer , and the main standard is 61.5 mm .