The bevel bit allows mild leverage, with a brass alloy lozenge to assist with salivation. The ring is larger on the 5" and 5.5" so the bit remains in proportion with the larger horse's head. Mouthpiece thickness: 16mm. Cheek height: 55mm (4.5", 5"), 70mm (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.