The white polypropylene plastic caps are available in a variety of sizes and come with PE F217 liners. The PE F217 liner is a good general-purpose liner material. It has a broad application base, chemical resistance, and is a good choice for acids, alkalis, solvents, alcohols, oils, household cosmetics, and aqueous products. The plastic caps are also ribbed for a better grip when twisting the cap on and off.