The L833S is a silver metal 58-400 smooth skirt unishell continuous thread closure with F217 liner. This closure includes an F217 foam liner, which will create an airtight seal when the lid is securely screwed on to the container. This closure fits a container with a 58-400 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.