This Superior Shade 16 Foot Square Shade Structure is made from high density, fire resistant Polyethylene material with UV stabilizers that is knit in a certain way as to ensure material will not unravel if cut. The frame is made of four 3.5 Inch diameter 11 gauge galvanized steel posts coated with UV-inhibited weather resistant powder coating. All steel parts are coated for rust protection. Surface mounted for stability.