Eggbutt from Bombers.

Eggbutt prevents the horse from being pinched in the lips/corner of the mouth by the bit rings and provides a more stable feeling against the horse. Eggbutt ensures that the bit remains still in the horse's mouth.

Barrel 20 is a common, jointed mouthpiece that has a nutcracker effect, which means it folds and presses on the horse's bars and tongue, distributing pressure over a larger area. When you take a rein contact, the bit wraps around the tongue, creating tongue pressure and reducing pressure on the bars because the bit cannot fold. This bit part is sharper than the Elliptical (three-piece with oval center) because the pressure is more concentrated on the tongue since this center part is smaller.