An object that sits in the horse's mouth and to which the reins are attached. Most bits are made of metal, but some have a mouthpiece synthetic material or leather. The mouthpiece of the bit must lie in the diastema (the stretch of mouth where the horse has no teeth between the incisors and the molars). The mouthpiece is attached to rings or shanks to which the reins attach. There are hundreds of different types of bit which can be matched to the horse's and the rider's experience, ability, and personality, and the activity or discipline. Regulations on the use of different types of bits vary between disciplines.