20mm Vial Septas, Teflon Silicone Septas, Pack of 50 Highest chemical resistance available. Teflon coating on one side of a solid white isoprene rubber septa. Manufactured in the USA. All stoppers require appropriate washing, rinsing, and sterilization, whenever applicable, to meet industry specific requirements. We do NOT sell sterile stoppers. 20mm vial septas are for serum vials with a 13mm hole opening and 20mm outside rim-to-rim outer diameter (13x20mm).