A Ring Cheek piece introduces poll pressure as well creating leverage on the mouthpiece. The 4 Ring has 2 rings on the bottom to adjust the amount of poll pressure and leverage you want.
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.
