The Curb Gag uses the concept of a Rope gag but instead of applying poll pressure, it is used to apply curb pressure from the second/bottom rein. Although poll pressure is not totally removed as there is a similar action to the Ring or Drop Cheek on the bit/top rein.
It is supplied with curb strap.
The Colin Miles is a great schooling bit with a 55mm centre piece creating greater tongue pressure and reducing bar pressure. The rings give the horse something to play with and help keep the horses attention on the bit.
This particular joint exerts more pressure than the Control Plate or Elliptical.