Protective Closure Crystal Clear Bags are ideal of photography and art. The protective closure feature ensures the adhesive will not come in contact with the contents when re-using the bag. Made from Biaxially Oriented Polypropylene (BOPP), a superior material that does not easily rip, tear, wrinkle, or fog like other plastics. Bag sizes indicate the opening side as the first dimension. ± 1/16 size tolerance. 1.6 Mil wall thickness.