Hollow Mouth Eggbutt
The jointed mouthpiece applies pressure to the tongue, lips, and bars with a "nutcracker" action. The hollow mouth is lighter than a standard solid mouthpiece. Due to it's larger surface area it spreads out the pressure. This bit may not fit comfortably in some horses' mouths if they are a little small.
The eggbutt rings almost eliminate the chance of the lips being pinched. It also provides a more stable and consistant contact on the mouth.