Our Cryogenic vialsare designed for storing biological materials at temperatures as low as -190°C. A silicone gasket between the polypropylene tube and cap assures a leakproof seal at all temperatures. The cap of the external thread vials has a flexible sealing lip at its top as well as an exclusive silicone seal. Together, the two form the best possible seal for ultra-low temperatures. Nonsterile vials do not include gasket or frosted marking area. All are standard 12.5mm diameter.