bar), or have an arched port in the center of varying height, with or without joints. Some have rollers, rings or small "keys" that the horse can move with its tongue. Mouthpieces may be smooth, wire-wrapped or otherwise roughened, or of twisted wire or metal.

Various types of metal or synthetic substances are used for bit mouthpieces, which may determine how much a horse salivates or otherwise tolerates a bit; a horse having a moist mouth is considered more relaxed and responsive. Commonly used metals include stainless steel