Jai Alai balls, also known as pelotas, are round, hard balls used in the sport of Jai Alai. They are made of rubber and are slightly larger than a baseball. The ball is thrown with a curved basket called a cesta, which is attached to the player's arm. The ball must be caught and thrown in one continuous motion, making it a very fast-paced game. The speed of the ball can reach up to 188 mph, making it one of the fastest sports in the world.