The L217WHH163 is a white PP plastic 53-400 smooth skirt lid with a printed universal heat induction seal (HIS) liner, already placed inside the cap. An HIS liner is a metallic disc that provides airtight, tamper-evident hermetic seal when an appropriate heat induction sealing process is applied. This liner can work with all types of plastic. For more information on heat induction sealing and available machinery, please read our article, How to use HIS liners and a heat induction sealing machine. This lid is made of polypropylene (PP), which means it has a high heat tolerance level and an excellent resistance to fatigue. This closure fits a container with a 53-400 neck finish. The first number refers to the diameter of the containers opening (in mm). The second number refers to the thread/style/depth of the closure's skirt. Please read 5 seals and how they make perfect liners for your container for more information on liner types.