A ball gag is usually made of rubber or silicone in the shape of a sphere with a strap passing through its diameter. The most common diameter is 1 3/4 inches, but other sizes can be found.
In use, the ball is strapped into the mouth behind the teeth, with the straps going around the head to secure it in place. If the ball is very large, it may be difficult to push it into place behind the teeth, or to remove it. A ball gag's purpose is more of humiliation rather than silence; the wearer can still be heard, but it renders their speech completely unintelligible, distorts their facial features, and, should the wearer attempt to talk, excessive drooling will result.
A wiffle gag is a simple ball gag that replaces the standard solid rubber ball with a light plastic ball similar to the one used for the game of floorball. This is normally seen in Japanese bondage contexts, and is generally safer because there is constant airflow. This is useful for asthmatics. Drooling can also be induced by pulling the gagged person's lip for a minute. Once drooling starts, it is almost impossible to stop. Some people use this as a way of emphasising that they are in control of the bound person. Also, some people find the sight of a gagged person drooling very erotic.