Color-code your sample vials. Thermo Scientific™ Nunc™ CryoTube™ Colored Caps are for use with Nunc internally threaded CryoTube vials and include a silicone gasket to provide the best seal. Nunc CryoTubes are the most widely used cryo vials in the world, stemming from the first cryo vials manufactured in the early 1960s. The well-proven design, the high certification level and the large portfolio of vials provide researchers with a choice of the vial best suited for their application and peace of mind that the sample can be retrieved viable and unharmed.