The Centaur® Professional D series contains all of the features a professional rider seeks:-Curved Mouthpiece allows the horse to swallow freely, encouraging relaxation.-Copper Inlay Mouthpiece encourages salivation.-Independently Moving Sides allows the rider to engage one side of the bit without affecting the opposite side. Due to the contagious nature of the equine disease EHV 1 and in accordance to biosecurity measures suggested by the American Association of Equine Practitioners we are unable to accept returns on bits.