Info from Manufacturer: All natural ingredients combined in a very special process make D'Addario Natural Rosin perfect for either horsehair or synthetic hair bows. Handsome packaging fits nicely in cases and the unique plastic channel provides an easy grip for students. Light or dark rosin All natural ingredients Plastic channel provides easy grip Suitable for horsehair or synthetic hair bows Designed and manufactured in the USA at our New York facility to the most stringent quality controls in the industry