Factors that affect the fit of the bit include both the length of the mouth overall, the length of the interdental space between the incisors and the molars where the bit rests on the bars (gums) of the horse's mouth, the thickness of the horse's tongue and the height of the mouth from tongue to palate. There is less room for error with a horse who has a short mouth, thick tongue and a low palate than with a horse who has a longer mouth, thinner tongue and a higher palate.