The rollers on this bit can help to prevent the horse taking a hold but can also encourage mouthing. The D-rings help with steering and prevent the bit from being pulled through the mouth. Mouthpiece thickness: 14mm. 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.