Blenheim Bib Martingale in Black. The Blenheim range is made from high quality leather that is cut by hand and stitched by craftsmen and features stainless steel fittings. The Bib Martingale offers an adjustable neck strap and girth loop. The Bib Martingale provides the same action as Running Martingale but can also help maintain a consistent rein contact as the bib prevents the reins being moved to far apart. The Martingale is useful for horses that raise the head too high to avoid the contact; if the horse raises the head above the contact, pressure is applied to the reins and therefore the bars of the mouth encouraging the horse to lower the head.