Another metal that is sometimes seen in bit making is aluminum. The aluminum bit trend started many years ago and still exists today, primarily in lower quality bits. Aluminum is not a particularly desirable metal for bit construction due to its light weight and unpalatable taste. Also, because aluminum oxidizes readily these bits may break unexpectedly. The lightness of these bits causes them to move too much in the horse's mouth and can cause the horse to have a diminished response to rein cues. Quality aluminum bits generally have shanks of a higher grade aluminum alloy and a mouthpiece made of some other material.