According to the USBC Rulebook, Chapter 7: Equipment Specifications and Certifications CAQ’s, page 115:
Can I use a ball with a crack in it?
If a crack is located within your track area, it is not permitted for use during USBC competition. A crack is defined as a narrow opening or crack of considerable length and depth usually occurring from some breaking or parting.
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So, if it is in the track area, it is not legal to use.