The Loose Ring Tube cheek pieces lies flat against the horse's face giving a more solid feel against the side of the face, while preventing pinching of the lips and the bit being pulled through the mouth. The mouthpiece is quite fixed in the mouth and concentrates pressure on the bars but the loose rings allow for a quick release.
A horse shaking its head when bit pressure is applied or its tongue trying to escape the bit are classic signs the horse has a sensitive tongue. With this in mind the McHardy was created, it has a medium port creating space for the tongue relieving pressure. The Buster Roller in the middle increases bar pressure and as a result lifting the horse's head and giving more control.