This flexible mouth rubber pelham has a thick and soft mouthpiece. Can be used with double reins or pelham roundings.Stainless Steel with Rubber Covering - Rubber covered bits generally have thicker mouths, making them softer and particularly suited to sensitive mouths. Available as mild, flexible rubber or treated with heat to product a harder rubber which has a slightly stronger action. It is important that the horse salivates effectively using rubber mouthpiece bits.