Tubes withstand centrifugation more than 12,000 rpm and fit rotors that accommodate 15 ml tubes. These tubes withstand temperatures from 121C to -80C., are made with virgin natural polypropylene, and free of RNase, DNase, and non-pyrogenic. Superior clarity and external graduations ensure accurate, reproducible lab results. Tubes have flat cap and frosted cap & side for marking with markers. The tubes can be used for repeated cap closures.