The L1384BKP4 is a black PP plastic 20-410 smooth skirt disc top cap with pressure sensitive (PS) liner. Disc top caps are made of two pieces: the skirt and the disc. To dispense product, you press on one side of the disc, causing the opposite to snap up. You can then reverse the process to store product. This cap comes with a pressure sensitive (PS) liner. Pressure sensitive liners are made from foamed polystyrene. When the cap (with liner installed) is affixed to the bottle, the liner adheres to the bottle's landing/orifice. Before product can be dispensed, the lid must be removed and the PS liner peeled off and discarded. 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 20-410 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.