The loose rings discourage the horse from leaning on the bit whilst the lozenge softens the contact and the copper helps encourage mouthing. Mouthpiece thickness: 16mm. Cheek height: 65mm. Stainless steel is the most common material for bits. Durable, easy to clean, tasteless and does not rust. Copper is used in the mouthpiece, creating warmth and encouraging salivation to keep the mouth soft.