The L461 is a black PP plastic 70-400 smooth skirt lid with 2-piece heat induction seal (HIS) liner (for PET and PVC containers only). This closure comes with a heat induction seal (HIS) liner, already placed inside the cap. An HIS liner is a metallic disk that provides an airtight, tamper-evident hermetic seal when an appropriate heat induction sealing process is applied. This liner can work with plastic or glass containers. 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 liner should only be paired with containers made of PET or PVC. 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 70-400 neck finish. The first number refers to the diameter of the container's 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.