May 25, 2011 · It is important to know that not all plastics are created equal. For instance, that 4 mil and 6 mil nstruction grade polyethylene sheeting in the nstruction aisle is the lowest grade of polyethylene sheeting available on the market at any given time. It is made from up to 25% post nsumer recycled goods, reground resins, and the HENAN OKAYolute least expensive resins that can be bought from any source in any location across the globe.