The fixed rings prevent pinching, whilst the brass alloy double joint distributes pressure over both the tongue and bars of the mouth to encourage mouthing and contact. Mouthpiece thickness: 14mm. Cheek height: 55mm (4.5", 5"), 75mm (5.5", 6"). Blue sweet iron mouthpieces oxidise easily to create warmth with a sweet taste which helps with bit acceptance and encourages salivation. Please note the blue colour will fade with use. Stainless steel is used for the cheeks due to it being durable, easy to clean and resistance to rust.