The curved mouthpiece on this bit allows more room in the mouth, making it suitable for horses with large tongues or small mouths. Mouthpiece thickness: 16mm. Cheek height: 50mm (4.5", 5"), 65mm (5.5"). 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.