Good for high heat applications (up to 200°C continuous), improved chemical resistance compared with natural rubber and autoclavable for sterile uses. Ideal for air- and moisture-sensitive chemistry procedures. After piercing with non-coring needle, rubber closes puncture, providing air and moisture-tight seal to protect contents of vessel or container from atmosphere. This closure has turnover flange molded to grip outside of container neck, promoting a double seal in conjunction with annular serrations on hollow plug. Annular serrations depress themselves against the inside wall of the bottle neck, making each serration a suction sealing point. Note: For extra security when using large bore transfer needles, fasten septum to bottle or flask opening with a wrap-it tie