Internally Threaded Cryo VialsThermo Scientific Nunc Internally Threaded Cryo Vials For cryogenic storage of cells, blood, serum and other biological specimens. Available with internal threads, external threads and round bottom, conical bottom, self standing and non standing varieties in sizes from 1. 0 to 4. 5 mL. Internally threaded Cryotubes are designed for vapor phase liquid nitrogen freezing while the external threaded vials are designed for mechanical freezing. Each case of