This 20 x 30 ft poly tarp is built for tough outdoor jobs where moisture and Uv exposure would destroy a lightweight cover. The 10 mil polyethylene fabric uses a 12 x 12 weave count and withstands over 8 kPa of water pressure, keeping lumber, firewood, equipment and construction materials dry in heavy rain. Reinforced hems with aluminum grommets spaced every 18 inches accept rope or bungee cords for a taut, snap-free stretch.