The blue alloy roller pelham oxidizes faster and easier compared to black sweet iron. It will rust when in contact with air, humidity and saliva.  This surface rust tastes sweet to horses and naturally stimulates additional saliva production, encouraging better acceptance of the bit.  The pelham cheeks offer a mild leverage option and improve the stability of the bit in the mouth. The smooth brass roller discs provide an additional comfort to certain horses by giving them something to play with, keeping their mouth quieter and more receptive to the rider’s aids.

Often times riders will use bit converters in order to maintain a single rein option.