This O-ring is made out of 5/16" diameter material. 2-7/8" outside diameter against the extra weight in the compactness of the ring allows for a more stable feel and quick release. Smooth, two-piece snaffle has a slight curve to the bars allowing the bit to rest comfortably across your horse's entire mouth. This mouthpiece is considered to be mild. | Professional's Choice O-Ring Snaffle | Size 5-1/4"