Coolaroo Custom Square Shade Sail, Charcoal, 18 by 18-Feet Heavy duty, professional grade shade fabric is made to block up to 95-percent of harmful uv rays Coolaroo fabric is fade resistant and will not mold or mildew Shade sails can withstand wind gusts and will not blow away like umbrellas or gazebos 10 year guarantee against damage caused by ultraviolet exposure For square or rectangle sail the stainless steel hardware kit #403737 is available