5" mouth. This bit was designed to decrease the discomfort at the corners of the horse's mouth. This bit will not pinch. The extra 3" rings at each end of the mouthpiece float independently to disperse the pressure across the lip and cheek making the horse more responsive to the riders cues. Attach the rein to the floating "D" ring outside the cheek rings. The mouthpiece is large enough to allow the rider to tug on a horse without injuring the bars.