Nalgene 2203 Large Narrow-Mouth PPCO (polypropylene copolymer) Bottles with Closure are resistant to most acids, bases and alcohols. For storing chemicals and standards, collecting and storing distilled water. The 4-and 8-liter sizes (B6761-2, B6761-3) have built-in shoulder loop for attaching an identification tag. B6761-1 comes without shoulder loop. NOTE: Before autoclaving, just set cap or closure on top of the container without engaging the threads. These containers can be used for long-term storage, but direct UV exposure should be avoided.