This 13mm vial stopper features a straight plug design made from ultra bromobutyl rubber, a premium-grade material valued in pharmaceutical applications for its excellent sealing capabilities and low permeability. Its gray composition ensures a secure barrier against moisture and gases, preserving the stability of liquid vial contents. Chemically inert, it minimizes the risk of interaction with medications, making it ideal for compounding and pharmaceutical use. Supplied non-sterile, this stopper is designed to provide reliable containment for a variety of liquid pharmaceutical products.