1. Material: Strong, medical-grade polypropylene, and can be repeatedly frozen and thawed

2. Non-sterile

3. Autoclavable to 121°C and freezable to -196°C, and can be stored in vapor phase liquid nitrogen

4. Universal screw threads, sealing ring cap

5. Fit cryogenic vials with either internal or external screw threads for quick and convenient classification           and visual identification

6. 6 colors: white, red, yellow, blue, green, and violet