The Riverstone line of shade cloths is designed to be an easy-to-use, shade-producing cloth that is UV stable and will last for several years in the hottest environments. All their woven shade cloths are proudly made from black woven polypropylene strands Each shade cloth comes with brass grommets for securing the shade cloth. The grommets are placed approximately 2 feet apart around the perimeter of each shade cloth. The percentage listed indicates the amount of shade that is being provided. This also reflects how tightly woven the shade cloths are.