Moving the rein between the main ring and bottom ring allows leverage. Sweet iron and copper encourages the horse to be softer in the mouth. The 5" and smaller sizes of this bit have smaller rings to ensure the two ring gag bit remains in proportion. Mouthpiece thickness: 16mm. Cheek height: 115mm (4.5", 5"), 145mm (5.5", 6"). Sweet iron mouthpieces are designed to oxidize to produce a sweet taste which helps with mouthing. The addition of copper to the mouth ensures the horse will not take up too much of a contact, ideal for horses that can take a hold. Stainless steel is used for the cheeks due to it being durable, easy to clean and resistance to rust.