The L207S is a white PP plastic 45-400 ribbed skirt child-resistant cap with F217 liner. Child-resistant caps are equipped with a locking mechanism that requires additional effort to open. To be designated as "child-resistant" these caps have undergone the requisite evaluations of a regulatory agency. This closure includes an F217 foam liner, which will create an airtight seal when the lid is securely screwed on to the container. 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 45-400 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.