The white write-on strip makes sample identification easier and more convenient. Nasco Whirl-Pak® bags are not autoclavable. Whirl-Pak® bags are sterilized with ethylene oxide gas. All Whirl-Pak® bags feature “PUNCTURE PROOF TABS.” This patented process extends the tape on the tab past the wire ends eliminating the sharp points which could puncture the bags, scratch a person’s hand, or puncture gloves. Resins used in the extrusion of film for Whirl-Pak® bags are approved for food contact. Bags are manufactured in accordance with the requirements for manufacturers of single service containers for milk and milk products, as specified by the Food & Drug Administration. Bags should not be used at temperatures above 180°F, 82°C. Bags can be frozen to any temperature, even liquid nitrogen. Careful handling is required after freezing.