The polyethylene film is made from pigmented resins so the black color is an integral part of the bag and not a printed layer. The result is an opaque bag providing maximum protection for samples that are sensitive to light. It is ideal for pharmaceuticals, spinal fluid, amniotic fluid, seasonings, flavors, food supplements, vitamins, marine life, and many other liquid or solid products. The 55-oz. (1,627 ml) bag is FDA approved for food contact. Film thickness is 2.5 mils (0.064 mm), box of 500.