Parenteral drug products must be stored in a container system that provides good container closure integrity (CCI) over shelf life for the purpose of preventing environmental contamination. This system typically comprises a glass vial, elastomer stopper, and an aluminum seal. USP Chapter &lt;1207&gt; <em>Packaging Integrity Evaluation &ndash; Sterile Products</em> discusses in detail methods to measure CCI to determine if the system can meet the maximum allowable leak limit (MALL) for its specific drug product (i.e., the smallest gap, or leak rate, that places quality at risk). Critical to achieving good CCI is proper capping of the vial with the stopper and seal, making sure that the compression level of the stopper is appropriate.