The smooth black PP disc top closures are made with a slight indent in the plastic top, which is designed to have a light amount of pressure applied to it in order to expose the orifice where the product can be dispensed. Disc cap made of polypropylene plastic are great for health and beauty product lines. They are a great way to dispense lotions,gels,shampoos,conditioners and more. It is mostly paired with plastic cylinder bottles or thinner diameter bottles.