Horse breast collars are pieces of equipment used to secure the saddle in place on a horse's back. They are typically made of leather or nylon and consist of a strap that goes across the horse's chest and attaches to the saddle, helping to prevent the saddle from sliding backwards or slipping off to the side during riding. Breast collars are commonly used in disciplines such as trail riding, barrel racing, and roping. They are available in a variety of styles and designs to suit different preferences and needs.