Also known as lug lids, lug caps, and twist caps, lug closures are the choice for a variety of products that are heat-processed and hot-filled in glass jars. Lugs are the equally spaced tabs around the skirt (under-rim) of the closure. Their purpose is to interlock with the interrupted tread of the container's finish (neck). Due to that interlocking, lug closures can be applied or removed with less than a full turn. Continuous-tread (C-T) closures, by contrast, interlock with the continuous thread of the container's finish and require at least a full turn to apply or remove. On the inside of lug closures is a compound (typically plastisol), essential in effecting a hermetic seal. When the closure is applied, the compound compresses around the lip (land) of the container, filling any void between the container's lip and the underside of the closure.
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