Dee/D Bits get their name from the shape of the bit rings. The end of the mouthpiece merge into a hinge, to which the D ring attaches. This shape stops the corner of the mouth from being pinched between the mouthpiece and the rings. They encourage turning, when the cue is given, by putting pressure on the outer cheek. Racing Ds are typically bigger in order to prevent the bit rings being pulled through the mouth. The D bit is ideal for children or novice riders. D ring mouthpieces do not slide like a loose ring, so they are usually fitted more closely than a loose ring, as this reduces friction back and forth across the mouth.
