The thickness of the bits vary a lot, and the thinner the bit, the sharper it is. However it isn t always the best solution for the horse to have a very thick bit. The thicker bits are heavy, and some horses do not like this. If the horse likes the thickness, but not the weight of it one can get a hollow bit of the same thickness, since they are lighter. On a horse with a small mouth, or a thick tongue it is best not to use a very thick bit since the horse might have a problem to hold it in the mouth.
Medium thickness is the best for most horses.
This is often a problem with rubber covered bits. They are covered with rubber to make them gentle for the horse, but they are usually quite thick. Also, horses often don t care for the taste of the rubber and will try to spit it out. The rings on the snaffle will also have an effect. Like described above the snaffle works so that when you pull on the left rein the bit slides over to the left side of the horses mouth, and the right ring will make contact in the corner of the mouth.