This polypropylene non-looped screw cap with "O" ring is compatible with all Axygen scientific screw top microcentrifuge tubes, including both skirted and non-skirted variations of the 0.5mL, 1.5mL, and 2mL microcentrifuge tubes. The O-ring closure is formulated and manufactured from a special compound resistant to chemicals such as anhydrous Ethyl Alcohol, Purified Ether, Hexane, Acetone, Chloroform, Acetonitrile, 40 percent Trifluoroacetic acid solution, and other chemicals used in most laboratories. The caps have extra long lips to help protect samples and ribs to allow one hand operation. Sterile. Color: Orange. Corning Axygen #: SCO-O-S.