The dee ring applies pressure to the horse's cheek on the opposite side of the face from the rein you pull to allow for better flexion Mouthpiece breaks over the bars at an angle to contact new nerves and add some tongue pressure for better control, while Golden Glide bushing ensure that the bit isn't going to pinch your horse's mouth Copper adds a sweet and sour taste for moisture and will also act as a pacifier for horses that chew on the bit Stage A bits are great for starting horses, training, or maintaining steady contact. Aspects include direct reining, non-leverage loose rings and dee rings with mouthpiece diameters 5/16" and over Mouth Size: 5" Mouth; Mouth Diameter: 7/16"; Mouth Material: Copper, Sweet Iron; Mouth Type: 3-Piece, Roller, Smooth; Horse Size: Horse