This bit works by putting pressure on the poll and the tongue. Attaching the reins to the lower ring will increase severity. Mouthpiece thickness: 15mm. Cheek height: 135mm. The EquiKind+ coating is thinner than a rubber mouthpiece making them more comfortable for horses that don't have room for a thick mouthpiece and ideal for sensitive mouths or horses that don't like metal in their mouths. Stainless steel is used due to it being durable, easy to clean and resistance to rust.