The indoor game was introduced in the United States and is played predominantly there, thus allowing polo in winter.
The field is 100 yards long and 50 yardswide, with wooden boards 4–4 1/2 feet (1.2–1.4 m) highto keep the ball in play.
The ball is inflatable leather, 4 1/2 inches in diameter and weighing at least 6 ounces. A team has three players instead of four as in the outdoor game.
Except for some minor rule changes, the indoor game is basically the same as the outdoor.