The L601BKH15 is a black PP plastic 89-400 ribbed skirt lid with a vented heat induction seal (HIS FS5-4) liner. 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. It will seal to the container and allow internal pressure to vent through the paper layer. This liner works best with plastic. PLEASE NOTE: We recommend that this liner NOT be paired with 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 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 89-400 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.