Sam Marsh Pelham mouthpiece features:

This bit is placed flat in the horse's mouth and turns 90 degrees. This improves the fixation in the horse's mouth and thus the comfort, making the horse lighter in the hand. Pelhams  mouthpiece consists of 1 piece and gives pressure on the tongue, layers and lips. The shape and thickness of the mouthpiece determine where the pressure will be. The straighter and thicker the mouthpiece, the more pressure on the tongue.