Made of medical grade polypropylene; Can be repeatedly frozen and thawed Self-Standing and external threads Vials have a white writing area and black graduations 1D barcode and human-readable numbers on the side Gamma radiation sterilized; DNase & RNase free, endotoxin-free, foreign DNA free Working temperature: stable from -196℃? to 121℃? Suitable for liquid nitrogen freezing 25/Bag, 500/Pack, 1000/Case