The L001Y is a yellow PP plastic 38-400 ribbed skirt hinged flip top dispensing cap with unprinted pressure sensitive (PS) liner and 0.25 inch orifice. Flip top dispensing caps have a hinged lid that snaps into place. Because it is made of polypropylene (PP), this hinged cap can be opened and closed thousands of times before breaking. The orifice opening is 0.25". 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 38-400 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.