You are buying 8 Ounces (by weight) of Sodium Sulfite. The item is in an 8 Fluid Ounce (by volume) Polypropylene bottle. Sodium Sulfite (Na2SO3); also known as Disodium Sulfite / Sulfurous Acid / Disodium Salt / Sulftech; has hundreds of uses. Bottles are made of sturdy polypropylene. The square, “space-saver” shape ensures that the bottles fit snugly on a shelf. The wide mouth makes for easy dispensing and stackability. To ensure a spill-free journey, the screw tops are heat-sealed and the bottles are sealed in plastic.