Heavy Duty Vacuum Bottle, PP bottle, white PP screw closure, TPE gasket Our most durable NALGENE bottle. Large, thick-walled bottle with wide mouth for extra-rugged service. Polypropylene bottle and white polypropylene closure with TPE gasket provide Leakproof† service. Withstand application of full vacuum for 24 hours at 20°C. Leakproof†/Autoclavable . NOTE: Before autoclaving, just set cap or closure on top of the container without engaging the threads.