The extraordinary strength safety and reliability of our Screw-Cap tube lets you perform procedures that simply can t be done with other tubes. Spin it store it transport it (even by air). Boil it irradiate it immerse it in the vapor phase of liquid nitrogen-it ll stand up to the test! Inside the screw cap our ethylene propylene O-Ring formsa secure and leakproof seal. Our screw cap s square threads won t strip-and they re on the outside of the tube so you minimize the risk of contaminating your sample-or letting it contaminate you. Our Screw-Cap tube is ideal for any sample-processing or storage application imaginable-and especially for working with valuable or hazardous cells and materials.