The Dee Ring is very similar in action to the Eggbutt, it will prevent pinching of the lips and gives a slightly more solid feel against the side of the face. It also prevents the bit being pulled through the mouth. The release is slower and some slight poll pressure is introduced.
The Elliptical is a 45 mm lozenge, it is stronger than the Control Plate due to it having a smaller surface area. Consequently, a horse using his tongue as a means of pushing against the bit and therefore taking control, will draw back and tuck his chin in, coming back to a better point of control.