Sterilized by gamma radiation, our advanced cryogenic tubes have an O-Ring screw cap for a positive, leakproof seal. They’re designed for safe storage of cells or biological fluids in the vapor phase of liquid nitrogen or any mechanical freezer. They’re ideal for sperm, serum or blood specimens, microbiological cultures, cell cultures, and hazardous or valuable samples.Our rugged, precision-molded copolymer and uniform wall construction will stand up to any current microcentrifuge. Plus, our tubes’ external threads prevent leaking even under the pressure changes of air transport. No tube offers more security to your sample!Sample Integrity- Sterilized by gamma radiation. Non-toxic and non-pyrogenic. Screw cap with internal O-ring forms a leakproof seal during processing and storage.Safe and Efficient- External thread eliminates material hangup and minimizes chance of contaminating you or your sample. Square threads won’t strip!Convenient- Conical design lets you retrieve your entire sample. Upright models stand without a rack. Molded ridges match racks (Cat. No. 4212), so you can open and close tube with one hand. Tubes fit all fixed angle head microcentrifuges (upright models require adapter Cat. No. 4212).Sturdy- Virtually unbreakable. Will withstand maximum G-forces of all current microcentrifuges when used with fixed angle heads.