The Dee ring is similar in action to the Eggbutt, it prevents pinching and gives a slightly more solid feel against the cheeks. This prevents the bit from being pulled through the mouth. The release is slower and some slight poll pressure is introduced.
The central barrel allows for a separation of reins aids, enabling a fine tuning of communication. The limited movement of the barrel allows the port to adjust to fit a wide range of mouth configurations. The adjustable port allows the horse to manoeuvre pressures between its tongue & bars.