Shires Medium Port Mouth Pelham. The port in this pelham provides extra area for the horse's tongue. Can be used with twin reins or Pelham roundings. Mouthpiece thickness is 14mm. Cheek height: 130mm (4.5-5), 140mm (5.5). Stainless steel is the most prevalent material used in bits. Durable, easy to clean, tasteless, and will not rust.