Eggbutt bit from Bombers.

The eggbutt bit prevents the horse from being pinched in the lips or corners of the mouth by the bit rings and provides a stable feel against the horse. It also prevents the bit from being pulled through the mouth. The release is somewhat slower and it also applies a little pressure on the poll.
A horse that shakes its head or sticks out its tongue are classic signs of a sensitive tongue. The McHardy mouthpiece was developed with this in mind. McHardy has a medium-high port that gives space for the tongue and reduces pressure on the tongue, and a roller in the middle that increases pressure on the bars.