This bit is made from hard rubber so it is not flexible but is still kind due to the thick mouthpiece. Mouthpiece thickness: 21mm. Cheek height: 65mm. Rubber covered mouthpieces are generally thicker, making them softer and particularly suited to sensitive mouths. Available as mild, flexible rubber or treated with heat to produce a harder rubber which has a slightly stronger action. It is important that the horse salivates effectively using rubber mouthpiece bits. Stainless steel is used due to it being durable, easy to clean and resistance to rust.