This bit is useful when control is an issue with the three rings offering leverage options to increase the severity. The 5" and smaller sizes of this bit have smaller rings to ensure the bit remains in proportion. Mouthpiece thickness: 15mm. Cheek height: 145mm (4.5", 5"), 180mm (5.5"). 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.