Square 18x18 ft Sun Sail Shade Cover - Green Effective Harmful UV Blocking Optimum Ventilation: The fabric enables cool air to penetrate the shade sail, offering an airy, comfortable, and well-ventilated space. Air Circulation Possible - Specially Knitted Polyethylene Fabric Ideal for Deck, Gardens, Patio, Backyards, Entryways, Pools & Children's Playing Area. Each corner of the shade has metal hooks and it takes minutes to set up