Ball used in tournaments
With the exception of National Championship Events, where the APTA Board makes the determination as to which ball will be used, Tournament Chairs of APTA Sanctioned Events could choose any APTA-approved ball, though only one brand was to be used throughout the tournament. Any player or players substituting another ball would be disqualified.
In addition, in National Ranking and Regional Ranking tournaments, no points would be awarded to those players who are disqualified.
It was reported that, whenever possible, the choice of ball should be indicated on the tournament entry form.
Source: Platform Tennis News, Winter 1996