These 20 mm snap-on chlorobutyl rubber stoppers are designed for secure sealing of pharmaceutical glass vials, commonly ranging from 10 ml to 100 ml in size. Manufactured from high-purity chlorobutyl rubber, they offer superior chemical resistance, low gas and moisture permeability, and excellent compatibility with a wide range of drug formulations. The snap-on design allows easy placement onto vial necks, ensuring a tight fit before sealing with an aluminum crimp for reliable containment. Supplied in packs of 25, these grey stoppers are ideal for pharmaceutical packaging applications requiring durability, sterility, and long-term product stability.