The Port allows enough room for the horse's tongue to fit comfortably under the flattened area of the port. Relaxation and chewing are a common reaction to this bit which is perfect for horses that won't tolerate tongue pressure who often react with excessive head shaking. The US Tandem is to be used with one set of reins. The pressure is distributed evenly between the horse's nose, lower jaw and poll. More rein action puts more pressure on the bars of the mouth. Suitable for horse's that are very sensitive in the mouth but can't be ridden with a Hackamore only. The US Tandem has black flexible tubing for the nose band instead of bright blue nylon rope found on regular Tandem.