The Eggbutt cheek piece prevents pinching of the lips and gives a solid feel against the side of the face. It also prevents the bit being pulled through the mouth. The release is slower than the loose ring and also introduces light poll pressure.
The Bombers Control Plate is set at 45° to follow the contour of the horses tongue. Best suits a horse that accepts tongue pressure.
For the horse that shakes its head up when in a snaffle. The control plate offers a larger surface area for the pressure to be distributed over.