This 18 ft. x 36 ft. Woven Poly Tarp is Waterproof, Mildewproof, Tear Resistant and Acid Resistant. 4.5 oz. per square yard, 9-10 mil thick, 10×10 weave count, grommets approximately every 36″. Finished size approximately 2% or 6″ shorter. Tarp is lightweight yet durable, manufactured from high-density polyethylene and woven into fabric and then laminated on both sides then finished by hemming the edges with poly twine inserted in hem. All seams and hems are heat sealed. UV Treated.