The bit is an important item of a horse's tack. It usually refers to the assembly of components that contacts and controls the horses mouth, and includes the shanks, rings, cheekpads and mullen, all described here below, but it also sometimes simply refers to the "mullen", the piece that fits inside the horses mouth. The mullen extends across the horses mouth and rests on the "bars", the region between the incisors and molars where there are no teeth. The bit is located on the horse's head by the , and which has itself several components to allow the most comfortable adjustment of bit location and control.