Steel chain in edge hem all around keeps wind from getting under, so these tarps stay down even in high winds.  Field proven to 65 mph.  Industrial 14 oz. vinyl-polyester fabric with UV and mildew inhibitors is fusion welded at every seam.  Strong double-stitched hem uses thread that is the best UV-resistant grade available.  Tarp is "circular" with 36 equal sides.  It's designed to cover only the circular dirt area, contributing to dirt moisture mangagement and allowing extended use.  Color is forest green.