The different sizes of plastic plugs used for sealing or closing bottles. These plugs come in various diameters to fit different types of bottles or containers. They're commonly used in industries like cosmetics, pharmaceuticals, and food and beverage packaging. Each size corresponds to the diameter of the bottle opening it's designed to seal. So, for example, a 22mm plug would fit a bottle with a 22mm opening, while a 40mm plug would fit a bottle with a 40mm opening. These plugs are crucial for maintaining the integrity and freshness of the contents inside the bottle by providing a tight seal. They're also often used for safety and hygiene purposes.