A thinner mouthpiece can make this bit a little stronger, however it may be more comfortable for horses with small mouths or large tongues. The fixed rings prevent pinching. Mouthpiece thickness: 12mm. Cheek height: 55mm (4.5", 5"), 75mm (5.5", 6"). Brass alloy mouth: Copper is alloyed with a harder metal to produce warm, durable mouthpieces which aid salivation. Stainless steel is used for the cheeks due to it being durable, easy to clean and resistance to rust.