The Eggbutt shape will prevent pinching of the lips. The release is slower and some slight poll pressure is introduced. The Eggbutt Gag is the gag version of the Eggbutt is stronger and will create more leverage on the mouthpiece whilst at the same time introducing more poll pressure.
The Bombers Control Plate is set at 45° to follow the contour of the horses tongue. Consequently, a horse who uses 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.