Crystalgen microcentrifuge tubes are easy to use, and designed to prevent evaporation, leakage, and accidental opening. Audible open & close pops seal tubes for boiling, freezing, centrifugation, and exposure to phenol/chloroform mixtures. The tube thickness is optimized for optical clarity and strength. Tubes are manufactured from 100% virgin polypropylene. Certified free of detectable RNase, DNase, DNA and pyrogens.