 Additionally, the shank or ring has a great impact on the action of the mouthpiece.Snaffles are generally considered the mildest, curbs and gags the harshest.It is difficult, therefore, to compare a harsher-type bit with a mild mouthpiece (such as a pelham with a rubber mullen mouth), and a milder-type bit with a harsher mouthpiece (like a thin snaffle with a slow twist).