Trust Sweet Iron Curb Gag Dr. Bristol BitA curb gag is similar to a gag but has a different effect. The pressure will now not be behind the ears but on the lower jaw chin. The cord runs under the chin and the cheekpieces are attached to the extra ring at the top. This bit is effective for strong, hot horses and is mainly used by show jumpers. This bit is not suitable for inexperienced riders. The Dr. Bristol mouthpiece is a double jointed mouthpiece with a flat insert. During relaxation,