A 2 Ring gag cheek piece introduces greater poll pressure as well as creating more leverage on the mouthpiece. The Colin Miles brass roller is a great schooling bit with a wide 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 Bit . 

The bluing on mouth is made from sweet iron. Sweet Iron is designed to  oxidize when it comes into contact with moisture; this oxidation process encourages salivation which improves acceptance of the bit. This process changes the bluing  of the ERS horse bit .