Billiard Practice Training cue ball for new snooker and pool players practice. a billiard ball is a small, hard ball used in cue sports, pool, and snooker. The number, type, diameter, color, and pattern of the balls differ depending upon the specific game being played. Various particular ball properties such as hardness, friction coefficient and resilience are important to accuracy. Great for game rooms, bars, sports match, leisure exercise, and players at all skill levels.