to resist tampering with the contents of containers , a plastic cap is provided with a foil liner . when the cap is seated on the container neck , the foil is caused to be sealed across the neck . to inhibit the foil from coming loose from the cap before closure a circumferential groove is formed in the inside of the skirt wall immediately below the cap top disc . the outer edge of the foil snaps into the groove but does not remain in the groove when the cap is removed for dispensing contents . a tab is formed extending out from the edge of the foil to be gripped by the consumer to remove the foil . this tab is folded over when the tab and cap are intact .