Excellent, versatile bit with 3 rein position options. It gives the rider the option to increase or decrease the amount of leverage the bit will provide when the reins are pulled because there is a choice of two positions to attach the reins to. If the reins are placed in the lower slot, the bit will have more curb action than the upper slot. The curb chain prevents the bit from rotating too far in the horse's mouth. When the reins are pulled back, the bit applies pressure to the bars of the mouth, the chin, and the poll. The ported mouth curves upwards to allow more room for the tongue, hence putting more pressure on the bars of the mouth. This makes the curb action more effective. Works well for horses that pull hard. Curb chain for extra leverage.