You chose the Ball size that you want. You can have the same size or even 2 different size balls. One really small and one as large as 3/4". What ever you want. Just check the Chart Below. These Circulars are all 316LVM Surgical Steel and all internally threaded, so there is no skimping on quality.

Gauge You Are Ordering	Smallest Ball Size that will fit
16 Gauge	Balls MUST be 1/8" or Larger
14 Gauge	Balls MUST be 1/8" or Larger
12 Gauge	Balls MUST be 5/32" or Larger
10 Gauge	Balls MUST be 3/16" or Larger
8 Gauge	Balls MUST be 1/4" or Larger
6 Gauge	Balls MUST be 1/4" or Larger
4 Gauge	Balls MUST be 5/16" or Larger
2 Gauge	Balls MUST be 5/16" or Larger
0 Gauge	Balls MUST be 7/16" or Larger
00 Gauge	Balls MUST be 7/16" or Larger
7/16" Gauge	Balls MUST be 1/2" or Larger
1/2" Gauge	Balls MUST be 5/8" or Larger