Polo is a team sport playe outdoors on horseback in which the objective is to score goals against an opposing team. Riders score by driving a white wooden or plastic ball (size 3–3.5 inches, weight 4.25–4.75 ounces) into the opposing team's goal using a long-handled mallet. Goals are only valid if the scoring rider is mounted. The traditional sport of polo is played outdoors, and each polo team consists of four riders and their mounts.